1. Any of various marine bivalve mollusks that attach to hard surfaces in intertidal areas with byssal threads, especially the edible members of the family Mytilidae and in particular Mytilus edulis, a blue-black species of the North Atlantic Ocean, raised commercially for food.
2. Any of numerous freshwater bivalve mollusks of the order Unionoida that burrow in the sand or mud of rivers, streams, and ponds.
3. Any of several similar bivalve mollusks, such as the zebra mussel.
[Alteration (possibly influenced by Dutch mossel) of Middle English muscle, from Old English muscelle, from Medieval Latin mūscula, from Latin mūsculus, sea mussel; see MUSCLE.]
(click for a larger image)mussel
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.