/kray"fish'/ , n. , pl. ( esp. collectively ) crayfish , ( esp. referring to two or more kinds or species ) crayfishes .
1. Also called crawdad, crawdaddy . any freshwater decapod crustacean of the genera Astacus and Cambarus, closely related to but smaller than the lobsters.
2. any of several similar marine crustaceans, esp. the spiny lobster.
Also, crawfish .
[ 1350-1400; alter. (by folk etym.) of ME crevis crevice krebiz CRAB 1 ]