plunge, plunging, plunged 1. To thrust into water, or into any substance that is penetrable; to immerse; to cause to penetrate or enter quickly and forcibly; to thrust; as, to plunge the body into water; to plunge a dagger into the breast. Also used figuratively; as, to plunge a nation into war. 2. The act of thrusting into or submerging; a dive, ... Found on http://www.wordinfo.info/words/index/info/view_unit/1705/2