Sus
Etymology
A clipping of suspicious or suspect, older British slang (as in the "sus laws" that let police stop suspected persons). It was mass-revived by the online multiplayer game Among Us (2020), where players accuse each other of being the impostor by calling them "sus."
adjective · /SUSS/
Suspicious or untrustworthy — seeming as though something is off or being hidden.
What it names
A quick flag for the feeling that a person, story, or situation doesn’t add up. Its usefulness is its low stakes: you can call something sus on a hunch, short of an actual accusation.
Example
He said he was at the library till midnight, which is a little sus given the library closes at nine.
Related idea
Milder than calling someone a liar: sus registers a suspicion, not a verdict.