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1.
The time it takes for two people to feel totally comfortable and start acting like their true selves in a relationship. Often times this is the time in which the pair will find out if they are really compatible or it was all just for fun and they were covering up their issues.
"Did you hear that Joe and Cindy broke up?"

"Yeah, totally the 8 month rule, those two were never gonna work, they were just high on the idea, and sex"
by fakethefunk November 08, 2011