sac

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

• noun A pouch or pouchlike structure in an organism, sometimes filled with fluid.
• noun A sacrifice fly.
• noun A sacrifice bunt.

from The Century Dictionary.

• noun A member of a tribe of Algonkin Indians, allied to the Foxes, who lived near the upper Mississippi previous to the Black Hawk war of 1832. The greater part are now on reservations.
• noun In law, the privilege enjoyed by the lord of a manor of holding courts, trying causes, and imposing fines. Also saccage.
• noun In bot., anat., and zoology, a sack, cyst, bag, bursa, pouch, purse, or receptacle of some kind specified by a qualifying word; a saccule; a saccus.
• noun Synonyms Sac, Saccule, Saccus, Sacculus. The first two are English, the last two Latin and only technically used, chiefly in special phrases. There is no such difference in meaning as the form of the words would imply, some of the largest sacs being called saccules or sacculi, some of the smallest sacs or sacci.

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

• noun (Ethnol.) See sacs.
• noun (O.Eng. Law) The privilege formerly enjoyed by the lord of a manor, of holding courts, trying causes, and imposing fines.
• noun See 2d sack.
• noun (Biol.) A cavity, bag, or receptacle, usually containing fluid, and either closed, or opening into another cavity to the exterior; a sack.

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

• noun A bag or pouch inside a plant or animal that typically contains a fluid.
• verb transitive, informal, video games To sacrifice (a creature).

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

• noun an enclosed space
• noun a member of the Algonquian people formerly living in Wisconsin in the Fox River valley and on the shores of Green Bay
• noun a structure resembling a bag in an animal
• noun a case or sheath especially a pollen sac or moss capsule