a small knoblike prominence or excrescence, whether natural or morbid; as, a tubercle on a plant; a tubercle on a bone; the tubercles appearing on the body in leprosy.-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.