An enlarged lymph node ("swollen gland") that is tender and painful, particularly in the groin and armpit (the axilla).

A feature of a number of infectious diseases including gonorrhea, syphilis, tuberculosis, and the plague; hence, the bubonic plague. The odd word bubo comes from the Greek boubon; meaning, "groin" or "swollen groin".

An inflamed swelling of lymph nodes in the areas of the armpits, neck, and other bodily parts: Dr. Roberts told Tony's cousin that his axillary bubo, or painfully enlarged lymph nodes, was probably a result of bubonic plague that is usually transmitted by the bite of fleas, probably from an infected rat, during his travels in Africa.