Petus is a term for a full-grown male who has a penis so small it could be the penis of a fetus.
"That guy showed me his penis in the bathroom. It was so small I'm sure it was a petus."
by New Year's In Tampa April 18, 2009
Acronym - People for the ethical treatment of the undead.
Hey, did you guys hear about that group protesting in front of gamestop? Yeah, it's PETU. I guess there's some new zombie shooting game released.
by v4p3d November 19, 2012