| water activity | <chemistry> An expression of the relative availability of water in a substance. Pure water has an water activity of 1.000. The water activity of a solution is one-hundredth its relative humidity. (09 Oct 1997) |
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| water adder | <zoology> The water moccasin. The common, harmless American water snake (Tropidonotus sipedon). Source: Websters Dictionary (01 Mar 1998) |
| water agrimony | <botany> A kind of bur marigold (Bidens tripartita) found in wet places in Europe. Source: Websters Dictionary (01 Mar 1998) |
| water aloe | <botany> See Water soldier. Source: Websters Dictionary (01 Mar 1998) |
| water arum | <botany> An aroid herb (Calla palustris) having a white spathe. It is an inhabitant of the north temperate zone. Source: Websters Dictionary (01 Mar 1998) |
| water barometer | <physics> A barometer in which the changes of atmospheric pressure are indicated by the motion of a column of water instead of mercury. It requires a column of water about thirty-three feet in height. Source: Websters Dictionary (01 Mar 1998) |
| water bath | In chemistry, a vessel containing water, in which a container holding a substance to be heated or evaporated can be immersed. (05 Mar 2000) |
| water battery | 1. <physics> A voltaic battery in which the exciting fluid is water. 2. A battery nearly on a level with the water. Source: Websters Dictionary (01 Mar 1998) |
| water bear | <zoology> Any species of Tardigrada. Source: Websters Dictionary (01 Mar 1998) |
| water-bearer | <astronomy> The constellation Aquarius. Source: Websters Dictionary (01 Mar 1998) |
| water bed | A mattress in the form of a closed rubber bag filled with water; used to prevent or treat pressure sores by equalizing the distribution of the patient's weight against the support. (05 Mar 2000) |
| water beech | <botany> The American hornbeam. See Hornbeam. Source: Websters Dictionary (01 Mar 1998) |
| water beetle | <zoology> Any one of numerous species of aquatic beetles belonging to Dytiscus and allied genera of the family Dytiscidae, and to various genera of the family Hydrophilidae. These beetles swim with great agility, the fringed hind legs acting together like oars. Source: Websters Dictionary (01 Mar 1998) |
| water bird | <zoology> Any aquatic bird; a water fowl. Source: Websters Dictionary (01 Mar 1998) |
| water blackbird | <zoology> The European water ousel, or dipper. Source: Websters Dictionary (01 Mar 1998) |