Sus is used as an abbreviated form of the word suspicious. Sus is typically used in a (dead) video game called “Among Us”. Sus is used when describing something or someone as suspicious.
Chad 1: I think I saw you stealsomething!
Chad 2: I would never do that.
Chad 1: Your pretty sus
An abbreviation of suspicious, popularized by the video game "Among Us" because of suspicious crew members that are secretly alien murderers looking to eat innocent crew members.
When suspicious actions are performed by certain individuals that lead you to doubt their credibility, sus is used as a shorthand to indicate to your fellow crewmembers that those individuals are behaving in a strange, off putting manner that may have arose as a result of their ineptitude in covert and protracted acts of deception!