Reference to gay male intercourse. Either mutual oral gratification until completion, mutual jerking off or doing each other in the pooper until you can't stand it any longer and finally blow your load, preferably on each other's faces.
A phrase that is used to excuse the natural rowdy behavior of young boys like getting dirty, being hyperactive, and playing rough with other boys. However, it has been disgustingly appropriated by misandrist gender ideologues who have perverted by falsely claiming it is used to excuse criminal activity boys and men do including rape, assault, and murder.
The closest thing to a female equivalent would be a girly girl.
What soccer moms say when their son has just done something AWFUL. This statement implies that any negative behavior should be excused on the grounds that boys are always doing things that are wrong, and need to be treated with a degree of leniency that borders on insanity.
Bystander: Oh my God, that kid is raping a nun!!
Soccer Mom: <Fake Laugh> Oh, well, you know. Boys will be boys. I'm sure he just had a hard day at school.