bladder

Short definition from Wiktionary

Noun

1. 1
   A flexible sac that can expand and contract and that holds liquids or gases.
2. 2
   Specifically, the urinary bladder.
3. 3
   A hollow, inflatable organ of a plant.
4. 4
   The inflatable bag inside various balls used in sports, such as footballs and rugby balls.
5. 5
   A container in the form of a flexible bag.
6. 6
   A container in the form of a flexible bag: A sealed plastic bag that contains wine and is usually packaged in a cask.
7. 7
   Anything inflated, empty, or unsound.

Verb

1. 1
   To swell out like a bladder with air; to inflate.
2. 2
   To store or put up in bladders.