any of various bivalve mollusks, especially certain edible species.Compare quahog, soft-shell clam.
Informal. a secretive or silent person.
Slang. a dollar or the sum of a dollar: I only made 60 clams a week.

verb (used without object), clammed, clam·ming.

to gather or dig clams.

Verb Phrases

clam up, Slang. to refuse to talk or reply; refrain from talking or divulging information: The teacher asked who had thrown the eraser, but the class clammed up.

Nearby words

  1. clairseach,
  2. clairton,
  3. clairvoyance,
  4. clairvoyant,
  5. clairvoyantly,
  6. clam diggers,
  7. clam up,
  8. clam-diggers,
  9. clam-flat,
  10. clam-shell

Origin of clam

1585–95; short for clam-shell, i.e., bivalve with a shell that clamps. See clam2, shell

Related formsclam·like, adjectiveclam·mer, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for clam up

clam up


(intr, adverb) informal to keep or become silent or withhold information




any of various burrowing bivalve molluscs of the genera Mya, Venus, etc. Many species, such as the quahog and soft-shell clam, are edible and Tridacna gigas is the largest known bivalve, nearly 1.5 metres long
the edible flesh of such a mollusc
informal a reticent person

verb clams, clamming or clammed

(intr) mainly US to gather clams
See also clam up

Word Origin for clam

C16: from earlier clamshell, that is, shell that clamps; related to Old English clamm fetter, Old High German klamma constriction; see clamp 1



verb clams, clamming or clammed

a variant of clem
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for clam up
Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with clam up

clam up

Refuse to talk or respond, as in Whenever she asks her teenager about his activities, he clams up. This term alludes to the tightly closed valves of a live clam. [Slang; early 1900s]


In addition to the idiom beginning with clam

  • clam up

also see:

  • happy as the day is long (as a clam)
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.