To measure or record the time taken by a process or activity. The runner clocked a time of 9.8 seconds in the 100-meter dash.
To hit or punch someone, especially in the face. He got angry and clocked him right on the jaw.
To notice or observe something. I clocked the way she was looking at him from across the room.
To reach or register (a particular speed, distance, or amount) as shown on an instrument. The jet clocked 700 miles per hour during the test flight.