river rule 

An imaginary river is around your group, conversation, building/house, messages, etc.. Everything said or done inside this "river" stays in it.

Kinda like what happens in Vegas stays in Vegas.

"Hey Jess, I gotta tell you something."
"Ok, shoot!"
"River Rule is now in effect, ok? This is serious."

river rule by BatmanOfTheOpera March 2, 2015

Two River Rule 

After crossing two or more rivers to get to your destination, sleeping or hooking up with other people is no longer considered "cheating" on your spouse and everybody is fair game.

If I fly to Germany for a business trip and leave my wife behind, I am ultimately crossing two rivers, therefore, sleeping with other women is not considered cheating, because I've crossed two rivers, putting the "Two River Rule" into effect

Two River Rule by Dre' October 16, 2012

3 river rule 

a rule stating that if you are more than 3 rivers away from the person you are dating then all faithfulness to your significant other is null and void. Synonymous with 50 mile rule.

Joe did not feel bad about cheating on his girlfriend because he knew he was covered under the 3 river rule.

3 river rule by inspire_d March 12, 2004