A sexual act or position in which 2 males simultaneously preform oral sex on each other. The term derives from the visual effect of the numeral: The top of the '6' and bottom of the '9' represent the penises while the bottom of the '6' and top of the '9' represent the mouths.
Very frequently, though incorrectly, conflated with 68
which is a similar act preformed my a male/female pair (the '6' representing the male and the '8' representing the female).
My wife and I heard about 69
ing from a gay couple, so we decided to try 68