The engagement in incestual sexual behavior between a brother and sister, often involving a third, unrelated participant. Often times, the encounter involves the use of the position known as the spit roast, with the sister (known as the annie) receiving the reproductive organ of the brother (known as the uncle jerry) in her mouth, while simultaneously receiving the reproductive organ of the third, unrelated participant in either her vagina or anus.
Dude, when I go to Boston this summer, I am going to round up Adam's mother and uncle and we are gonna have one giant annie uncle jerry.
by Half-Brew April 4, 2008