noun

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