Verb
fall or drop suddenly, usually to evade some danger
Source: WordNetHe turned his head, reacted in a microsecond, and hit the deck just before a hundred-mile-an-hour fastball zipped past his ear and clanged into the wire backstop. Had the pitch been another inch lower or a few miles an hour faster, he would have been beaned and, at that speed, possibly killed. Lis Wiehl
Curran and I mixed about as well as glycerin and nitric acid: put us together, shake a bit, and hit the deck as we exploded. Ilona Andrews
The soldiers hit the dirt when they heard gunfire Source: Internet