Source : Webster's Revised Unabridged Dictionary (1913)

Quahog \Qua"hog\, Quahaug \Qua"haug\, n. [Abbrev. fr.
   Narragansett Indian poqua[^u]hock.] (Zo["o]l.)
   An American market clam ({Venus mercenaria}). It is sold in
   large quantities, and is highly valued as food. Called also
   {round clam}, and {hard clam}.

   Note: The name is also applied to other allied species, as
         {Venus Mortoni} of the Gulf of Mexico.

Clam \Clam\, n. [Cf. {Clamp}, {Clam}, v. t., {Clammy}.]
   1. (Zo["o]l.) A bivalve mollusk of many kinds, especially
      those that are edible; as, the long clam ({Mya arenaria}),
      the quahog or round clam ({Venus mercenaria}), the sea
      clam or hen clam ({Spisula solidissima}), and other
      species of the United States. The name is said to have
      been given originally to the {Tridacna gigas}, a huge East
      Indian bivalve.

            You shall scarce find any bay or shallow shore, or
            cove of sand, where you may not take many clampes,
            or lobsters, or both, at your pleasure. --Capt. John
                                                  Smith (1616).

            Clams, or clamps, is a shellfish not much unlike a
            coclke; it lieth under the sand.      --Wood (1634).

   2. (Ship Carp.) Strong pinchers or forceps.

   3. pl. (Mech.) A kind of vise, usually of wood.

   {Blood clam}. See under {Blood}.

Source : WordNet®

Venus mercenaria
     n : an edible American clam [syn: {quahog}, {quahaug}, {hard-shell
         clam}, {round clam}, {Mercenaria mercenaria}]