Spanish-moustache 

While your sex partner is positioned doggy-style you put your thumb up her/his ass and when he/she turns around you draw a line just above her/his lip with your thumb.
PS.
If a thick line is left it may also be referred to as "giving a Hitler"

i totally gave that chick a Spanish-moustache last night. Then she kicked me in the balls.

Spanish-moustache by Spanklord October 18, 2008