look up any word, like bangarang:
 
1.
The day in which no matter the excuse, your girlfriend permits you the opportunity for anal sex. Fortunately for the men this is a fact!! Ref:-The laws of co-habitation, 1883- mcMiller, Brian. Book 3 chapter 4, section 69.
IE: Jeff- " hey honey guess what day it is?"

Random hot chick- "hump day?"

Jeff- " kinda! It's my b-day which includes birthday anal, plz adopt the position."
by Rules of engagement December 03, 2013