Clock

To clock someone means to spot or figure out something about them that they were not openly presenting. In transgender contexts it usually means recognizing that someone is trans when they are trying to be read simply as their gender. Being clocked can be a real safety concern for trans people in hostile settings, and it can also touch on gender dysphoria and the pressure to "pass." In drag culture the term is lighter, meaning that an audience sees through the illusion of the performance. More broadly, "clock" can mean catching or noticing anything someone did not mean to reveal, as in "she clocked that I was nervous." Context shapes whether it lands as neutral, playful, or threatening.