The sex position in which the girl is laying flat (emphasis on laying completely flat) on her belly with penis entry from behind. This position often enables the female to work the muscles in the region resulting most likely in an overpleasurable time for the man involved, thus causing premature ejaculation.
I nailed Lucy in prone bone last night!
A sexual position where the woman lays flat on her stomach with her legs together and the man, on his knees, stradles her legs just below the butt, sitcking his penis into her now tightly-squeezed vagina.
Janine was napping face down in the nude when Rick climbed on and gave her the prone bone.