coldcock
To strike someone, knocking them down and, possibly, rendering them unconscious. The burglar would have escaped too, had a passerby not coldcocked him. Everyone was stunned when that scrawny nerd coldcocked the bully.
coldcock someone
to knock someone unconscious. He hit him once and looks like he coldcocked him. She cold-cocked him with her walking stick.
coldcock
tv. to knock someone out. The clerk coldcocked the would-be robber with a champagne bottle.