swimmeret

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One of the paired abdominal appendages of many aquatic crustaceans, such as shrimp and lobsters, that are used for swimming and in females for carrying eggs.

from The Century Dictionary.

• noun In Crustacea, a swimming-foot; a pleopod; an abdominal limb or appendage usually adapted for swimming, and thus distinguished from the ambulatory or chelate thoracic limbs, fitted for walking or seizing.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) One of a series of flat, fringed, and usually bilobed, appendages, of which several pairs occur on the abdominal somites of many crustaceans. They are used as fins in swimming.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun zoology In decapods such as lobsters, one of the legs primarily used for swimming but also used for brooding the eggs (except in prawns) and catching food.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun one of the paired abdominal appendages of certain aquatic crustaceans that function primarily for carrying the eggs in females and are usually adapted for swimming