Blad″der (�), n. [OE. bladder, bleddre, AS. bl�dre, bl�ddre; akin to Icel. bla�ra, SW. bläddra, Dan. blære, D. blaar, OHG. blātara the bladder in the body of animals, G. blatter blister, bustule; all fr. the same root as AS. blāwan, E. blow, to puff. See Blow to puff.]
1. (Anat.) A bag or sac in animals, which serves as the receptacle of some fluid; as, the urinary bladder; the gall bladder; — applied especially to the urinary bladder, either within the animal, or when taken out and inflated with air.
2. Any vesicle or blister, especially if filled with air, or a thin, watery fluid.
3. (Bot.) A distended, membranaceous pericarp.
4. Anything inflated, empty, or unsound. “To swim with bladders of philosophy.” Rochester.
Bladder nut, orBladder tree(Bot.), a genus of plants (Staphylea) with bladderlike seed pods. — Bladder pod(Bot.), a genus of low herbs (Vesicaria) with inflated seed pods. — Bladdor senna(Bot.), a genus of shrubs (Colutea), with membranaceous, inflated pods. — Bladder worm(Zoöl.), the larva of any species of tapeworm (Tænia), found in the flesh or other parts of animals. See Measle, Cysticercus. — Bladder wrack(Bot.), the common black rock weed of the seacoast (Fucus nodosus and F. vesiculosus) — called also bladder tangle. See Wrack.