What does "bladder" mean?

Additional senses

1. 2.(Bot.) A distended, membranaceous pericarp.
2. 3.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 (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.
3. 4.To swell out like a bladder with air; to inflate. [Obs.] G. Fletcher.
4. 5.To put up in bladders; as, bladdered lard.