Courtesy Flash: Occurs when a strong, strictly platonic, friendship forms between an average male and extremely attractive female. The male wants to bang the female incredibly bad, but usually the female is hung up on ex-boyfriends, or too emotionally unavailable for the male friend to take advantage. Under these circumstances, the female will need the male friend to reach out to, and in turn the male friend will keep trying to bang the female, because of the attention he is receiving from her. The female will recognize this, which will make her feel ill of depriving this weary emotional soldier, her good friend, his sexual dues, and will reward him with a random flash for the time he has put in. Thus the Courtesy Flash was born; to repay the male who has no chance of banging the one he desires, yet just deserves to see some fuckin' amazing titties.
Davon: So I Laura and I went to the lake yesterday, she and I are such great friends!
Mika: Holy shit dude, she has the biggest cans I have ever been in the presence of.
Davon: Damn, you're right. I want to bang her so bad it's all I can think about. She keeps teasing me with the courtesy flash. I can't just ignore the possibility of seeing some grade A boobies at random, just for talking about her ex boyfriends new girlfriend. Her boobies are so nice.