When a man who is normally quite kind and level headed, goes completely moody and rude for a couple of days. They will have all the moodiness and irritability of a girl on her period, hence MANstrual cycle.
Person 1: Jeez, what's going on with Jim? He's never this moody.
The manstrual cycle occurs during a man's special time of the month, when the male becomes extremely irritable and eager for intercourse. But due to his irritability, this week is the time when the most masturbation occurs.
Girfriend- What's wrong with (your name here)
Best Friend- Oh, nothing really, he's on his manstrual cycle.
Girlfriend- Oh, I guess I better lay off, and have sex with him.