The Collaborative International Dictionary of English v.0.48:

Bladder \Blad"der\, v. t. [imp. & p. p. Bladdered; p. pr. &
   vb. n. Bladdering.]
   1. To swell out like a bladder with air; to inflate. [Obs.]
      --G. Fletcher.
      [1913 Webster]

   2. To put up in bladders; as, bladdered lard.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bladder \Blad"der\ (bl[a^]d"d[~e]r), n. [OE. bladder, bleddre,
   AS. bl[=ae]dre, bl[=ae]ddre; akin to Icel. bla[eth]ra, SW.
   bl[aum]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.]
   [1913 Webster]
   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.
      [1913 Webster]

   2. Any vesicle or blister, especially if filled with air, or
      a thin, watery fluid.
      [1913 Webster]

   3. (Bot.) A distended, membranaceous pericarp.
      [1913 Webster]

   4. Anything inflated, empty, or unsound. "To swim with
      bladders of philosophy." --Rochester.
      [1913 Webster]

   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 (Zool.), 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 Fucus vesiculosus) --
      called also bladder tangle. See Wrack.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bladder
    n 1: a distensible membranous sac (usually containing liquid or
         gas) [syn: bladder, vesica]
    2: a bag that fills with air

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "bladder":
   air bubble, bag, ball, balloon, bleb, blister, blob, blood blister,
   boll, bolus, bubble, bulb, bulbil, bulblet, bulla, cap and bells,
   coxcomb, ellipsoid, fever blister, fob, geoid, globe, globelet,
   globoid, globule, glomerulus, gob, gobbet, knob, knot, motley,
   oblate spheroid, orb, orbit, orblet, pellet, pocket, poke,
   prolate spheroid, rondure, sac, sack, slapstick, soap bubble, sock,
   sphere, spheroid, spherule, vesicle