1. A condition, usually resulting in pain and dysmenorrhea, characterized by the abnormal presence of functional endometrial tissue outside the uterus, frequently as cysts containing altered blood.
2. The presence and growth of functioning endometrial tissue in places other than the uterus that often results in severe pain and infertility.
3. The presence of uterine lining in other pelvic organs, esp. the ovaries, characterized by cyst formation, adhesions, and menstrual pains.