When a man's dick does not go straight out when fully erect, but rather leans one direction or is curved or bent in an odd way.
Jessica was going to have sex with Mike but his leaning tower of penis proved to be too strange for Jessica.
A variation of the Eiffel Tower.
As with the Eiffel Tower, this sexual act involves three participants: two men and a woman. One man is getting fellated, by the woman, whilst the other man is penetrating her vagina or anus.
Mid-coitus, the two men diagonally high-five each other, thus creating the lean.
Hey Mike, Amy is talking like she wants to get slammed by the Leaning Tower of Penis tonight, you down?