Mactra \Mac"tra\, n. [NL., fr. Gr. ? kneading trough, fr. ? to knead.]

(Zo["o]l.) Any marine bivalve shell of the genus Mactra, and allied genera. Many species are known. Some of them are used as food, as Mactra stultorum, of Europe. See Surf clam, under Surf.

Source: Webster's Revised Unabridged Dictionary (1913)