http://www.biology-online.org/dictionary/Vesicle defines a vesicle as follows: A small cyst or sack containing gas or fluid.

In cell biology it defines a bubble-like membranous structures that stores and transports cellular products and digests metabolic wastes within the cell.

In physiology, it’s a membranous pouch within an axon terminal that stores and releases neurotransmitters.

In phycology, it means a floating gas-filled bubble or bladder-like structure in algal cells.

Mycology defines a vesicle as a bubble-like sack in fungus where zoospores mature and are eventually released,

In pathology it is known as a small fluid-filled lesion or blister beneath the skin.