n. & v.
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 a shy or withdrawn person.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.
[ 16th c.: app. f. clam a clamp ]