When you're not gay, but are sexually attracted to a single male.
Originated when a straight man fell for the luscious cheeks of a gay boy named Timmy, despite his sexuality having always been straight, and has continued to be nothing but straight, besides the one with the luscious cheeks.
Timmy : ill suck your dick
Straight man : God damnit im straight but I just cant resist that fat ass, I must be timmysexual