—n.
1 any bivalve mollusc, esp. the edible N. American hard or round clam (Mercenaria mercenaria) or the soft or long clam (Mya arenaria).
2 colloq. a shy or withdrawn person.
—v.intr. (clammed, clamming)
1 dig for clams.
2 (foll. by up) colloq. refuse to talk.
Etymology: 16th c.: app. f. clam a clamp
Useful english dictionary. 2012.