| tropical mask | A bronze-coloured pigmentation, probably produced by hormone imbalance, occurring in gradually increasing areas on the face, neck, and chest in persons exposed continuously to the tropical sun; similar to chloasma of the temperate zone, but intensified because of strong sunlight. Synonym: tropical mask. (05 Mar 2000) |
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| mask | 1. A cover, or partial cover, for the face, used for disguise or protection; as, a dancer's mask; a fencer's mask; a ball player's mask. 2. That which disguises; a pretext or subterfuge. 3. A festive entertainment of dancing or other diversions, where all wear masks; a masquerade; hence, a revel; a frolic; a delusive show. "This thought might lead me through the world's vain mask." (Milton) 4. A dramatic performance, formerly in vogue, in which the actors wore masks and represented mythical or allegorical characters. 5. A grotesque head or face, used to adorn keystones and other prominent parts, to spout water in fountains, and the like; called also mascaron. 6. In a permanent fortification, a redoubt which protects the caponiere. A screen for a battery. 7. <zoology> The lower lip of the larva of a dragon fly, modified so as to form a prehensile organ. Mask house, a house for masquerades. Origin: F. Masque, LL. Masca, mascha, mascus; cf. Sp. & Pg. Mascara, It. Maschera; all fr. Ar. Maskharat buffoon, fool, pleasantry, anything ridiculous or mirthful, fr. Sakhira to ridicule, to laugh at. Cf. Masque, Masquerade. Source: Websters Dictionary (01 Mar 1998) |
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| mask of pregnancy | <medicine> A dark discolouration of the skin, usually local; as, Addison's melasma, or Addison's disease. Melasmic. Origin: NL, fr. Gr. Black spot. Source: Websters Dictionary (01 Mar 1998) |
| mask shell | <zoology> Any spiral marine shell of the genus Persona, having a curiously twisted aperture. Source: Websters Dictionary (01 Mar 1998) |
| Hutchinson's mask | The sensation experienced in tabetic neurosyphilis as if the face were covered with a mask or with cobwebs. (05 Mar 2000) |
| shadow mask | <microscopy> Also Aperture mask. In colour video monitors, a finely perforated or striped metal plate that is located between the three electron guns and the phosphor screen. The mask ensures that the electron beams carrying the R, G, and B signals land on the corresponding phosphors at every point in the picture. (05 Aug 1998) |
| nonrebreathing mask | A mask fitted with both an inhalation valve and an exhalation valve so that all exhaled gas is vented to the external atmosphere and inhaled gas comes only from a reservoir connected to the mask. (05 Mar 2000) |
| ecchymotic mask | A dusky discoloration of the head and neck occurring when the trunk has been subjected to sudden and extreme compression, as in traumatic asphyxia. (05 Mar 2000) |
| laryngeal mask | A tubular oropharyngeal airway with an inflatable rim at the distal end that when inflated creates an airtight seal immediately above the larynx. (05 Mar 2000) |
| luetic mask | A dirty brownish yellow pigmentation, blotchy in character, resembling that of chloasma, occurring on the forehead, temples, and sometimes the cheeks in patients with tertiary syphilis. (05 Mar 2000) |
| macrocytic anaemia tropical | The macrocytic, megaloblastic anaemia of tropical sprue. (05 Mar 2000) |
| paraparesis, tropical spastic | Subacute paralytic myeloneuropathy occurring endemically in tropical areas such as the caribbean, colombia, india, and africa, as well as in the southwestern region of japan; associated with infection by type I human lymphotropic retrovirus (HTLV-I). Toxic nutritional factors have largely been ruled out as the cause of this syndrome, the primary clinical feature of which is progressive weakness of the legs and lower body. (12 Dec 1998) |
| sprue, tropical | A malabsorption syndrome occurring in the tropics and subtropics. Protein malnutrition is usually precipitated by the malabsorption, and anaemia due to folic acid deficiency is particularly common. Administration of antibiotics (especially tetracycline) and folic acid usually results in remission. (12 Dec 1998) |
| tropical | 1. Of or pertaining to the tropics; characteristic of, or incident to, the tropics; being within the tropics; as, tropical climate; tropical latitudes; tropical heat; tropical diseases. 2. [From Trope] Rhetorically changed from its exact original sense; being of the nature of a trope; figurative; metaphorical. "The foundation of all parables is some analogy or similitude between the tropical or allusive part of the parable and the thing intended by it." (South) Tropic month. See Lunar month, under Month. Tropic year, the solar year; the period occupied by the sun in passing from one tropic or one equinox to the same again, having a mean length of 365 days, 5 hours, 48 minutes.0 seconds, which is 20 minutes.3 seconds shorter than the sidereal year, on account of the precession of the equinoxes. Origin: Cf. L. Tropicus of turning, Gr. See Tropic. Source: Websters Dictionary (01 Mar 1998) |
| tropical abscess | <gastroenterology> An area of abscess formation (liquefaction necrosis) in the liver due to infection of the organ with amoebae. See: amoebiasis. (05 Feb 1998) |
| tropical acne | <dermatology> A severe type of acne of the entire trunk, shoulders, upper arms, buttocks, and thighs; occurs in hot, humid climates. (05 Mar 2000) |