1. A small rounded projecting part or outgrowth, such as a wartlike excrescence on the roots of some leguminous plants or a knoblike process in the skin or on a bone.
2. Pathology. A nodule or swelling, especially a mass of lymphocytes and epithelioid cells forming the characteristic lesion of tuberculosis.

[Latin tūberculum, diminutive of tūber, lump. See tuber.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.