Definition of blue crabs:
(n) :
Any crab of genus Callinectes
(n) :
especially of species Callinectes sapidus of eastern US
(n) :
Any member of either of two groups of crab:
(n) :
A crab of species Portunus pelagicus
(n) :
(by ellipsis) Any of several species of crab with three-part vernacular names. (See Derived terms and Related terms below.)
(n) :
Used other than figuratively or idiomatically: see blue crab.