Anatomy, Zoology .

a membranous sac or organ serving as a receptacle for a fluid or air.

urinary bladder.

Pathology . a vesicle, blister, cyst, etc., filled with fluid or air.

Botany . an air-filled sac or float, as in certain seaweeds.

something resembling a bladder, as the inflatable lining of a football or basketball.

an air-filled sac, usually made to resemble a club, used for beatings in low comedy, vaudeville, or the like.

noun

bag , blister , inflate , pocket , pouch , sac , vesicle