SOMF can be used to denote domination over another person
Facial sittings became popular in developing countries as a form of sexual intercourse which didnt require condoms. This was believed to be a way to prevent the spread of STD's and prevent unwanted pregnancies.
The abbreviation became popular with college students through the social networking site Facebook.
Some Girl; -sits on his face-
SOMF is primarily used as an indicative of sexual attraction, or as an act of sexual dominance.
Used in conjunction with Twitter, It is often stylised as #SOMF.