The definition of man up is:
be a man, take responsibility for your actions
A: My girlfriend is pregnant. I think I will break up with her.
B: What?! You need to man up. You should marry her!
When Jean forgot to pick his mother up from the airport, he manned up instead of lying, and she appreciated his honesty.
When William cheated on his wife, he thought manning up would be too difficult, so instead he continued to lie to her.
man up is only used for men.
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