To descend or plunge head first into water; thrust the body suddenly into water or other fluid; plunge deeply: as, to dive for shells.To make a plunge in any way; plunge suddenly downward or forward, especially so as to disappear: as, to dive down a precipice or into a forest.To plunge or enter deeply into something that engrosses the attention; engage deeply in anything: as, to dive to the bottom of a subject; to dive into the whirl of business.To explore by diving.n. A descent or plunge head first into water or other fluid; a “header”: as, a dive from a spring-board.n. A sudden attack or swoop: as, to make a dive.n. A disreputable place of resort, where drinking and other forms of vice are indulged in, and, commonly, vulgar entertainments are given: so called because often situated in basements or other half-concealed places into which the resorters may “dive” with little risk of observation.