a. Any of various predominantly marine crustaceans of the division Brachyura within the order Decapoda, characterized by a broad flattened cephalothorax covered by a hard carapace with a small abdomen concealed beneath it, short antennae, and five pairs of legs, of which the anterior pair are large and pincerlike.
b. Any of various similar related crustaceans, such as the hermit crab or king crab.
c. A horseshoe crab.
a. A crab louse.
b. crabsSlang Infestation by crab lice.
The maneuvering of an aircraft partially into a crosswind to compensate for drift.