To shan someone is to sexually harass a person in a social setting such as in a club, a bar, a house party, ... in an unashamed and perverted
fashion. Often
done by virgins and closet gays as a way to appear as "playas" in
front of their peers.
Dude I went clubbing with this douchebag the other
day, and he just totally attempted to shan some
girl. She ran away crying and he was like "bro she's totally lesbo, she's lucky I
even wanted to shan her".