What does "tubercle" mean?

Tubercle: (Med.) A small mass or aggregation of morbid matter; especially, the deposit which accompanies scrofula or phthisis. This is composed of a hard, grayish, or yellowish, translucent or opaque matter, which gradually softens, and excites suppuration in its vicinity. It is most frequently found in the lungs, causing consumption. Tubercle bacillus (Med.), a minute vegetable organism (Bacillus tuberculosis) discovered by Koch, a German physician, in the sputum of consumptive patients and in tuberculous tissue, and believed to be the exciting cause of tubercles and tuberculosis.