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.”
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 (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 Fucus vesiculosus) -- called also bladder tangle. See Wrack.