hypertrophy

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A nontumorous enlargement of an organ or a tissue as a result of an increase in the size rather than the number of constituent cells: muscle hypertrophy.
2. v. To grow or cause to grow abnormally large.

Century Dictionary and Cyclopedia

1. n. In pathology, an enlargement of a part of the body from excessive growth or multiplication of its elements; specifically, an enlargement due to growth of the individual elements, as distinguished from hyperplasia, where there is a multiplication of the cellular elements.
2. n. Figuratively, excessive growth or accumulation of any kind.
3. n. In botany, a general term for all cases of excessive growth and increased size in the organs of plants, whether the increase is general or in a single direction. It includes enlargements, or swollen and thickened conditions, which usually result from a disproportionate formation of the cellular tissue as contrasted with the woody framework of the plant, as in the rootstocks of the cultivated carrots, turnips, etc.; elongations, as of roots searching for water; and enation, or excessive development, consisting in the formation of supplementary lobes or excrescences from various organs.
4. To become hypertrophous or enlarged from excessive nutrition.

Wiktionary

1. n. countable, medicine An increase in the size of an organ due to swelling of the individual cells
2. n. 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.
3. v. intransitive, of a tissue or organ : To increase in size

GNU Webster's 1913

1. n. (Med. & Biol.) A condition of overgrowth or excessive development of an organ or part; -- the opposite of atrophy.

WordNet 3.0

1. n. abnormal enlargement of a body part or organ
2. v. undergo hypertrophy