penis coffin
Surrendering one's penis by dating someone who is incapable of having sex with (see robbing the grave).
John: Did you hear Robbie's dating a woman who's 72 years old?
Matt: Isn't he like 38?
John: Yeah, he better get a penis coffin because he's robbing the grave.
Matt: Isn't he like 38?
John: Yeah, he better get a penis coffin because he's robbing the grave.