n. The common name of the small fluviatile long-tailed decapod crustaceans of the genera Astacus and Cambarus; especially, in Great Britain, the Astacus fluviatilis; and by extension, some or any similar fresh-water crustacean. See cuts under Astacidæ and Astacus.n. The name in the west of England and among the London fishmongers of the small spiny lobster, Palinurus vulgaris. Also called sea-crawfish.To move backward or sidewise like a crawfish; hence, to recede from an opinion or a position; back out or back down.n. One who backs out from a position or undertaking, especially in politics.