1) Clam 2) Marine edible bivalve 3) Weighs up to six pounds 1) Clam 
• (n.) A gigantic clam (Glycimeris generosa) of the Pacific coast of North America, highly valued as an article of food.
(species Panopea generosa), marine invertebrate of the class Bivalvia (phylum Mollusca) that inhabits the sandy muds of the intertidal and shallow ... [1 related articles]
A long-neck, slightly crunchy sweet clam
Ge'o·duck noun [ American Indian name.] (Zoology) A gigantic clam ( Glycimeris generosa ) of the Pacific coast of North America, highly valued as an article of food. 
[n] - a large edible clam found burrowing deeply in sandy mud along the Pacific coast of North America
noun a large edible clam found burrowing deeply in sandy mud along the Pacific coast of North America; weighs up to six pounds; has siphons that can extend to several feet and cannot be withdrawn into the shell