1. slang To catch, apprehend, or arrest someone. After nearly three months on the run, police in Arkansas finally nailed the two fugitives. I heard Jimmy was nailed in Chicago last night. He'd better not squeal on us!

2. slang To catch someone out; to expose someone, as in a lie or a criminal or dishonest act. The undercover investigative journalist nailed the CEO in an attempt to bribe a state senator. I got my story mixed up, and my parents ended up nailing me in a lie.