1. The application of hand sanitizer (from the base to the tip, hence the name) to ones genitals before or after a particularly questionable bout of intercourse (though a post-coital 'base up' is less likely to result in unwelcome friction).
2. In reference to the sexual encounter itself, whereby you engage in risky business and will likely require the application of 'Base Up' in the near future.
3. As a noun referring to the sanitiser itself.
"I didn't use a condom, better base up"
"Should we base up before going to the clubs?"
"Who used all the base up?"
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).