A complete menstrual cycle of a girl you are having sex with. Each cycle you are constantly scared that she is not going to get her period and be pregnant. This is not necessarily a complete month it is any amount of time that you are scared and worried about a girl getting pregnant. When a girl gets her period, the scare cycle is finished.
"Dude I don't know I'm really worried about my girlfriend we are still in a scare cycle cause the condom broke" or "I just finished my scare cycle after that one-night stand I had"