Wiktionary
alt. A condition in which menstruation occurs, but the flow of the discharge is blocked n. A condition in which menstruation occurs, but the flow of the discharge is blocked
Wikipedia
Cryptomenorrhea or cryptomenorrhoea, also known as hematocolpos, is a condition where menstruation occurs but is not visible due to an obstruction of the outflow tract. Specifically the endometrium is shed, but a congenital obstruction such as a vaginal septum or on part of the hymen retains the menstrual flow. A patient with cryptomenorrhea will appear to have amenorrhea but will experience cyclic menstrual pain. The condition is surgically correctable.
The patient usually presents at the age of puberty when the commencement of menstruation blood gets collected in the vagina and gives rise to symptoms.