An unwritten book about laws that males must abide by.
1. Don't date your bestfriend's ex.
2. Don't backstab your bestfriend.
3. Bros before hoes.
4. Talk about girl's tits and twats a lot so you don't look gay.
5. Never joke about a guy's sister or mom.
6. Ball tap someone back for revenge.
And so on...
Greg went against the male handbook. He is dating Katelyn even though his bestfriend Andrew broke up with her in the Spring.