Yep, “suss” is a real word, short for “suspect.” “The detective could suss a new acquaintance in record time.” Can you? I discreetly suss people all the time, perhaps because they precipitate writing. American detectives would use the word “perp”. “Alexander quickly sussed the key to the riddle.” Alexander is one of my students, and he likes to tell me riddles, which I seldom suss. This word is a shortened version of “suspect,” from the French suspecter or directly from the Latin suspectare, meaning “to mistrust.” Word perfect will question “suss”. “Suss” can be used as a noun, verb, or adjective. source – word genius.com