Pronunciation: (thī'mus), [key]
—pl. -mus•es, -miPronunciation: (-mī). [key] Anat.
a ductless, butterfly-shaped gland lying at the base of the neck, formed mostly of lymphatic tissue and aiding in the production of T cells of the immune system: after puberty, the lymphatic tissue gradually degenerates. Also called thy'mus gland".
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.