center punch

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A tool with a sharp point used in metalworking to mark centers or center lines on pieces to be drilled.

Century Dictionary and Cyclopedia

1. n. A tool consisting of a small piece of steel with a hardened point at one end, used for making an indentation, such as to mark the center of a hole to be drilled or a circle to be struck, or as a center of revolution in a lathe. Also called dot-punch and prick-punch.

Wiktionary

1. v. to create a small hole or indentation in a workpiece as a guide in preparation for drilling
2. n. countable a device used to create a small indentation in preparation for drilling a hole
3. n. countable the small indentation created by such a device

GNU Webster's 1913

1. A punch for making indentations or dots in a piece of work, as for suspension between lathe centers, etc.
2. A punch for punching holes in sheet metal, having a small conical center to insure correct locating.

WordNet 3.0

1. v. make a small hole in something as a guide for a drill
2. n. a tool with a conical point that is used to make indentations in metal (especially to mark points for drilling)