| back | 1. Being at the back or in the rear; distant; remote; as, the back door; back settlements. 2. Being in arrear; overdue; as, back rent. 3. Moving or operating backward; as, back action. Back charges, charges brought forward after an account has been made up. Back filling, the retrograde movement of a man or body of men, without changing front. Back stream, a current running against the main current of a stream; an eddy. To take the back track, to retrace one's steps; to retreat. 1. In human beings, the hinder part of the body, extending from the neck to the end of the spine; in other animals, that part of the body which corresponds most nearly to such part of a human being; as, the back of a horse, fish, or lobster. 2. An extended upper part, as of a mountain or ridge. "[The mountains] their broad bare backs upheave Into the clouds." (Milton) 3. The outward or upper part of a thing, as opposed to the inner or lower part; as, the back of the hand, the back of the foot, the back of a hand rail. "Methought Love pitying me, when he saw this, Gave me your hands, the backs and palms to kiss." (Donne) 4. The part opposed to the front; the hinder or rear part of a thing; as, the back of a book; the back of an army; the back of a chimney. 5. The part opposite to, or most remote from, that which fronts the speaker or actor; or the part out of sight, or not generally seen; as, the back of an island, of a hill, or of a village. 6. The part of a cutting tool on the opposite side from its edge; as, the back of a knife, or of a saw. 7. A support or resource in reserve. "This project Should have a back or second, that might hold, if this should blast in proof." (Shak) 8. The keel and keelson of a ship. 9. <chemical> The upper part of a lode, or the roof of a horizontal underground passage. 10. A garment for the back; hence, clothing. "A bak to walken inne by daylight." (Chaucer) Behind one's back, when one is absent; without one's knowledge; as, to ridicule a person behind his back. Full back, Half back, Quarter back, players stationed behind those in the front line. To be or lie on one's back, to be helpless. To put, or get, one's back up, to assume an attitude of obstinate resistance (from the action of a cat when attacked). To see the back of, to get rid of. To turn the back, to go away; to flee. To turn the back on one, to forsake or neglect him. Origin: As baec, bac; akin to Icel, Sw, & LG. Bak, Dan. Bag; cf. OHG. Bahho ham, Skr. Bhaj to turn, OSlav. Bg flight. Cf. Bacon. Source: Websters Dictionary (01 Mar 1998) |
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| back aperture | <microscopy> The exit pupil of a microscope objective lens. The objective lens back aperture, which can be examined with a phase telescope or by inserting a Bertrand lens, displays the conoscopic interference figure and diffraction patterns. (05 Aug 1998) |
| back cross | <genetics> A crossing of a heterozygous organism and one of its homozygous parents. (09 Oct 1997) |
| back focal length | <microscopy> As measured on the principal axis, from the second lens vertex to the back focal point of the lens. It is not the equivalent of the focal length. (05 Aug 1998) |
| back focal plane | <microscopy> The plane, normal to the lens axis, situated at the back focus of a lens. (05 Aug 1998) |
| back injuries | General or unspecified injuries to the posterior part of the trunk. It includes injuries to the muscles of the back. (12 Dec 1998) |
| back lens | <physics> In any compound lens (a lens system composed of more than one lens element), the last lens through which the light passes is called the back lens. It may be a single simple lens, a doublet, or triplet. See: front lens (05 Aug 1998) |
| back mutation | <molecular biology> A mutation that causes a mutant gene to revert to its original wild-type base sequence. Compare: forward mutation. (09 Oct 1997) |
| back of foot reflex | The foot being firmly supported on its inner side, a sharp tap on the dorsal tendons causes extension of the second to the fifth toes. Synonym: back of foot reflex, dorsum of foot reflex. (05 Mar 2000) |
| back pain | A continuous pain located in the back, usually below the cervical level. For lower back pain or pain in the lumbar region, low back pain is available. (12 Dec 1998) |
| back pain, low | Symptoms in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area. The low back, or lumbar area, functions in structural support, movement, and protection of certain body tissue. (12 Dec 1998) |
| back pressure | Pressure exerted upstream in the circulation as a result of obstruction to forward flow, as when congestion in the pulmonary circulation results from stenosis of the mitral valve or failure of the left ventricle. (05 Mar 2000) |
| back teeth | All teeth posterior to the canines. (05 Mar 2000) |
| back-action plugger | An instrument for condensing gold foil or amalgam in areas that cannot be reached directly. (05 Mar 2000) |
| back-knee | Hyperextension of the knee, the lower extremity having a forward curvature. Synonym: back-knee. (05 Mar 2000) |
| adolescent round back | Osteochondrosis of the vertebral epiphyses in children. (12 Dec 1998) |
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| broadest muscle of back | <anatomy, muscle> Origin, spinous processes of lower five or six thoracic and the lumbar vertebrae, median ridge of sacrum, and outer lip of iliac crest; insertion, with teres major into posterior lip of bicipital groove of humerus; action, adducts arm, rotates it medially, and extends it; nerve supply, thoracodorsal. Synonym: musculus latissimus dorsi, broadest muscle of back. (05 Mar 2000) |
| pain, back | Symptoms in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area. (12 Dec 1998) |
| regions of back | The topographical regions of the back of the trunk, including the vertebral region, sacral region, scapular region, infrascapular region, and lumbar region. Synonym: regiones dorsales. (05 Mar 2000) |
| muscles of the back | The muscles of the back in general, including those attaching the shoulder girdle to the trunk posteriorly, the posterior serratus muscles, and the erector spinae. Synonym: musculi dorsi, dorsal muscles. (05 Mar 2000) |
| poker back | Arthritis and osteitis deformans involving the spinal column; marked by nodular deposits at the edges of the intervertebral disks with ossification of the ligaments and bony ankylosis of the intervertebral articulations, it results in a rounded kyphosis with rigidity. Synonym: Bechterew's disease, poker back, Strumpell's disease. (05 Mar 2000) |
| hog's-back | <geology> A hogback. Source: Websters Dictionary (01 Mar 1998) |
| hollow back | Accentuation of the lumbar curvature of the spine. (27 Sep 1997) |
| push-back procedure | A surgical manoeuvre designed to reposition the soft palate posteriorly and reestablish velopharyngeal competence. (05 Mar 2000) |
| stickle-back | <zoology> Any one of numerous species of small fishes of the genus Gasterosteus and allied genera. The back is armed with two or more sharp spines. They inhabit both salt and brackish water, and construct curious nests. Synonym: sticklebag, sharpling, and prickleback. Origin: OE. & Prov E. Stickle a prickle, spine, sting (AS. Sticel) + back. See Stick, and cf. Banstickle. Source: Websters Dictionary (01 Mar 1998) |
| straight back syndrome | <syndrome> Loss of the normal concavity of the thoracolumbar spine with a narrowed anteroposterior chest dimension, resulting compression of the heart between spine and sternum, and consequent prominent precordial pulsations, an ejection murmur, and radiologic evidence of a widened cardiac silhouette (pancaked heart). (05 Mar 2000) |
| superficial back muscles | Muscles originating from the vertebral column and having their fleshy bellies located in the back, but inserting onto the appendicular skeleton of the upper limb or the ribs. They are not innervated by dorsal primary rami of spinal nerves, as are the deep or true muscles of the back; includes the trapezius muscle (innervated by spinal accessory nerve) and latissimus dorsi, rhomboids, levator scapulae, and thoracic muscles (innervated by ventral primary rami of spinal nerves, or derivatives thereof). (05 Mar 2000) |
| deep muscles of back | Muscles of the back innervated by the dorsal primary rami of spinal nerves; includes erector spinae, transversospinalis, interspinal, and intertransverse muscles; excludes the superficial back muscles which are appendicular and are innervated by ventral rami, and the trapezius, innervated by the spinal accessory nerve. Synonym: true muscles of back. (05 Mar 2000) |
| diamond-back | <zoology> The salt-marsh terrapin of the Atlantic coast (Malacoclemmys palustris). Source: Websters Dictionary (01 Mar 1998) |
| double back cross | A mating that is a back cross at each of two loci of interest; of special value and importance in linkage analysis. (05 Mar 2000) |