Upon realization that one's sexual partner has started their menstrual cycle during the act of vaginal intercourse, a Bloody Geraldo is when a man swipes a desired number of fingers on said bloody vagina and proceeds to smear the blood across the area underneath his partner's nose; thus, she is left with a dripping mustache that resembles FOX News' anchor Geraldo Rivera.
"You wouldn't believe what I did last night, dude."
"Oh yeah, what this time?"
"I was fucking this chick and next thing I know she starts bleeding all over my dick."
"Ew that's gross dude"
"Not as gross as me giving her a Bloody Geraldo afterwards."