WordNet sense 1 (a clam that is usually steamed in the shell):

soft-shell clam, long-neck clam, steamer clam

WordNet sense 2 (a ship powered by one or more steam engines):

steamship

WordNet sense 3 (an edible clam with thin oval-shaped shell found in coastal regions of the United States and Europe):

Mya arenaria

WordNet sense 4 (travel by means of steam power):

steam