(dys- + Gr. mn month + rhein to flow) painful menstruation.
difficult and painful menstruation ... (13 Nov 1997) ... 
Painful periods
Pain before or during menstruation resulting from cramps of the uterus, colon and small intestine.
Dysmenorrhoea is pain with menstrual periods. The pain usually manifests itself in the lower abdomen or the small of the back.
dysmenorrhea, dysmenorrhoea (British) 1. Difficult and painful menstruation. Synonym: menorrhalgia. 2. Pain in association with menstruation. One of the most frequent gynecological disorders, it is classified as primary or secondary. This disorder is the greatest single cause of absence from school and work among menstrual-age women.