Mostly seen in Snapchat or Instagram stories, SU stands for "Swipe Up." Usually leads to a link of some sort or is used to direct people to chat with them.

A pick me is a woman that is willing to do anything for male approval. She will embarrass or throw other women under the bus to achieve this goal. The unfortunate thing about a pick me is usually the men they are trying to seek approval from are of poor quality and treat women badly, leaving little real benefit for the pick me.

it means STRAIGHT UP

calling of the Wu-Tang Clan

A way to say "Shut Up" on AIM or AOL Instant Messanger.

And abbreviation for shut up. Or STFU; an Abbreviation for shut the fuck up

SU is short for Super Unicorn. This one of a kind creature has been living for the past six centuries and knows about everything (except computers because he was busy preaching philosophical lessons when computer science was advancing). Many people believe that SU does not exist but historical sightings reveal that the creature may indeed be living among us for a very long time. SU was last spotted in the country of India, more specifically in the state of Maharashtra, according to certain unreliable sources.

Anecdotal evidence suggests that this creature is very similar to male human beings in terms of physical appearance.
He is known to possess certain powers which include Victory Dance, Intellect Beam, Emotional Torture, and Future Sight. He is also known to be a very wise and mature creature who offers advice to anyone who asks for it (and anyone who does not).
SU is known to have made and lost many friends in his long life so he appears to be rather recluse at times. He has been seen hanging out with turtles and tortoises often. The slow animals live a long life, very much like him, which enhances their friendship.
SU is known to be a social creature with anti social tendencies. To remain hidden from the prying eyes of the world and still maintain his original identity, he takes names with initials S.U. and tries to blend in with humans. He makes sure that he does not develop deep and strong bonds with most people because he is sure to outlive them.