1)To not behave like a child and to not behave like a woman.
2)To know what masculinity is and what testosterone does.
3)To be an adult male in the truest sense of his manhood.
1)Dude is a MOMMAS BOY, dude needs to man up.
2)Dude is on estrogen, dude doesnt know how to man up.
3)Dude does not mess around, you better man up.
Girl: Yeah he won't do it! Says he's a bad ass baller but won't just go for it. Man up dude.
Guy: Nevermind $20. I put a 50 spot on the fact he pussies out and doesn't do it.
When some boy or a man act very feminized and has behavior that is more appropriate for the female gender like gesturing or liking some things that it is not usually for guys to like ( such as makeup, fashion, etc.).When that boy or a man decided to change and to start acting and liking things that guys usually like(such as football ,beer etc) we could say that he Man up himself
John: Remember my neighbor Jack?
Joseph: Of course,that guy who everyone thinks is gay because of his effeminacy?
John,Yeah that guy,he actually Man up himself,he started to gym,he got muscles and he started to go on football matches
Joseph: Wow,he really man up himself