three one rule 

a rule that states that guys can date 3 grades up and 1 grade down during high school. anything lower and he would be considered pedo-ish.

Senior: Hey, whose that girl you were talking to a little while ago?
Junior: Shes a sophomore.
Senior: Crap! three one rule.

three one rule by John Slate May 2, 2009

one five three rule 

Unspoken but widely understood rule regarding selecting a public urinal, specifically if there are five urinals to choose from. If all are unoccupied you choose the one on the far left (1). If this one is occupied you choose the far right one (5). If both are occupied you choose the center one (3). The object is to maximize the space between yourself and anybody else who currently has their shlong out.

urinator 1) "Hey buddy, one five three rule. Scoot over."

*scoots over*

urinator 2) "Sorry, wasn't thinking"

one five three rule by skid mark vz March 8, 2008