vesicle

noun7

1. •
   A membrane-bound compartment found in a cell.
2. •
   A small bladder-like cell or cavity.
3. •
   A small sac filled with juice, one of many constituting the pulp of a fruit such as an orange, lemon, or grapefruit.
4. •
   A small sac or cyst or vacuole, especially one containing fluid. A blister formed in or beneath the skin, containing serum. A bleb.
5. •
   (usually and especially) Such a blister that is less than 5 mm in diameter.
6. •
   A pocket of embryonic tissue that is the beginning of an organ.
7. •
   A small cavity formed in volcanic rock by entrapment of a gas bubble during solidification.

   • It frequently contains holes, or vesicles, especially nearer the surface of a flow where gas has escaped. — 2004