(countable, medicine) An increase in the size of an organ or tissue due to the enlargement of its individual cells.

(uncountable, bodybuilding) Increase in muscle size through increased size of individual muscle cells; a result of weightlifting, and other exercise. It differs from muscle hyperplasia, which is the formation of new muscle cells.

(intransitive, of a tissue or organ) To increase in size.

(by extension) To enlarge or extend.