Definition of clamshells:
(n) :
The shell of a clam.
(n) :
Any object that, in (literal or figurative) resemblance to the shell of a clam, has a hinge on one edge and two surfaces that close together.
(n) :
In food service, the closing box (usually styrofoam but sometimes cardboard) given to consumers with takeout food.
(n) :
A hinged case for a video tape, cassette tape, or video game cartridge.
(n) :
A dredging bucket with hinges like the shell of a clam.
(n) :
(often attributive) Any object with some other resemblance to either one or both halves of the shell of a clam.