| half-moon | 1. The moon at the quarters, when half its disk appears illuminated. 2. The shape of a half-moon; a crescent. "See how in warlike muster they appear, In rhombs, and wedges, and half-moons, and wings." (Milton) 3. An outwork composed of two faces, forming a salient angle whose gorge resembles a half-moon; now called a ravelin. 4. <zoology> A marine, sparoid, food fish of California (Caesiosoma Californiense). The body is ovate, blackish above, blue or gray below. Synonym: medialuna. Source: Websters Dictionary (01 Mar 1998) |
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| half-ray | <geometry> A straight line considered as drawn from a center to an indefinite distance in one direction, the complete ray being the whole line drawn to an indefinite distance in both directions. Source: Websters Dictionary (01 Mar 1998) |
| half-reactions | <chemistry> The two parts of an oxidation-reduction reaction, one representing oxidation, the other reduction. (09 Jan 1998) |
| half-tetrad analysis | <genetics> The analysis of tetrad chromosomes (a pair of homologous chromosomes, thus four total chromosomes) after recombination when only half of the tetrad (two of the four chromosomes) can be analysed. (13 Nov 1997) |
| half-time | The time, in a first-order chemical (or enzymic) reaction, for half of the substance (substrate) to be converted or to disappear. Compare: half-life. (05 Mar 2000) |
| half-value layer | <radiobiology> The thickness of a specified material (usually a specific absorber), which attenuates a beam of radiation so that the exposure rate or absorbed dose rate at a specified point is reduced by half. (20 Sep 2002) |
| halfbeak | <zoology> Any slender, marine fish of the genus Hemirhamphus, having the upper jaw much shorter than the lower. Synonym: balahoo. Source: Websters Dictionary (01 Mar 1998) |
| halfer | 1. One who possesses or gives half only; one who shares. 2. A male fallow deer gelded. Source: Websters Dictionary (01 Mar 1998) |
| halfway house | A facility for individuals who no longer require the complete facilities of a hospital or institution but are not yet prepared to return to independent living. Specialised residences for persons who do not require full hospitalisation, and are not well enough to function completely within the community without professional supervision, protection and support. (20 Sep 2002) |
| halibut | <marine biology> A large, northern, marine flatfish (Hippoglossus vulgaris), of the family Pleuronectidae. It often grows very large, weighing more than three hundred pounds. It is an important food fish. Alternative forms: holibut. Origin: OE. Hali holy + but, butte, flounder; akin to D. Bot, G. Butte; cf. D. Heilbot, G. Heilbutt. So named as being eaten on holidays. See Holy, Holiday. Source: Websters Dictionary (01 Mar 1998) |
| halibut liver oil | <marine biology> The fixed oil obtained from the fresh or suitably preserved livers of halibut species of the genus Hippoglossus (family Pleuronectidae); a supplementary source of vitamins A and D. (05 Mar 2000) |
| halichondriae | <marine biology> An order of sponges, having simple siliceous spicules and keratose fibres. Synonym: Keratosilicoidea. Origin: NL, fr. Gr, sea + cartilage. Source: Websters Dictionary (01 Mar 1998) |
| halide | <chemistry> A salt of a halogen. (05 Mar 2000) |
| halieutics | <marine biology> A treatise upon fish or the art of fishing; ichthyology. Origin: L. Halieuticus pertaining to fishing, Gr. Source: Websters Dictionary (01 Mar 1998) |
| haliographer | One who writes about or describes the sea. Source: Websters Dictionary (01 Mar 1998) |