any of several huge clams of the family Tridacnidae, inhabiting the shallow waters of coral reefs in the tropical Indo-Pacific, as Tridacna gigas: some may weigh more than 500 lb. (225 kg)
Word origin
[1945–50]
Examples of 'giant clam' in a sentence
giant clam
The pearl produced by the horse conch is brown; that produced by the giant clam is beige.
Times, Sunday Times (2013)
Giant clams snap shut 60ft below the surface as our shadows paddle above them.