The shell of a clam.

Any object that has a hinge on one edge and two surfaces that close together, resembling the shell of a clam, and can refer to a dredging bucket or a closing box given to consumers with take-out food.

(often attributive) An object resembling one or both halves of a clam shell, or an outdoor amphitheater with a semi-circular acoustic backdrop.

(manufacturing) To deform a die in a shape resembling the shell of a clam, as a result of uneven extrusion pressure.

To dig out by means of a clamshell (dredging bucket).

To compress or flatten underwater debris so as to avoid blocking a channel.

(transitive, intransitive) To open or close by means of a hinge, similar to the way a clamshell opens and closes.