Bladder \Blad"der\, n. [OE. bladder, bleddre, AS. bl?dre, bl?ddre; akin to Icel. bla?ra, SW. bl["a]ddra, Dan. bl[ae]re, D. blaar, OHG. bl[=a]tara the bladder in the body of animals, G. blatter blister, bustule; all fr. the same root as AS. bl[=a]wan, 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, or Bladder 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 (Zo["o]l.), the larva of any species of tapeworm (T[ae]nia), 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.

Source: Webster's Revised Unabridged Dictionary (1913)