coscarse

A colloquial reflexive verb, mostly used in Spain, meaning to notice or catch on to something, often something someone was trying to hide ("se coscó del engaño"). Informal, conversational register.

• Se coscó de que le estaban mintiendo. — He caught on that they were lying to him.
• Nadie se coscó de que faltaba dinero en la caja. — Nobody noticed that money was missing from the register.
• Al final se coscó del plan y lo arruinó todo. — In the end she caught on to the plan and ruined everything.

Always used reflexively with de (coscarse de algo) — dropping the reflexive pronoun doesn't work; darse cuenta is the more universally understood equivalent outside Spain.