An elater is a cell (or structure attached to a cell) that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In plants that do not have seeds, they function in dispersing the spores to a new location.
Any beetle of the family Elateridæ, having the habit, when laid on the back, of giving a sudden upward spring, by a quick movement of the articulation between the abdomen and thorax; -- called also click beetle, spring beetle, and snapping beetle.
The active principle of elaterium, being found in the juice of the wild or squirting cucumber (Ecballium agreste, formerly Motordica Elaterium) and other related species. It is extracted as a bitter, white, crystalline substance, which is a violent purgative.