Wiktionary
alt. A narrow hole drilled or punched into a surface, to facilitate the insertion of a wider screw, nail, drill bit, or other bore tool. n. A narrow hole drilled or punched into a surface, to facilitate the insertion of a wider screw, nail, drill bit, or other bore tool.
Wikipedia
A pilot hole is either a small hole drilled into a material to guide a larger drill to the appropriate location and ease the job of the larger drill, to allow for the insertion of another hole making tool, such as a knockout punch, that will produce the final size hole, or, in wood or plastic, to locate, guide, and provide clearance for a self threading screw to prevent damaging the material or breaking the screw.
Usage examples of "pilot hole".
The spot was cutting along a circular path centered on a pilot hole.
A quick sniff verified that the distinctively acid smell of acetylene still hissed from the pilot hole, but he had to thumb the striking wheel five or six times before the waterlogged apparatus finally rewarded him with a spark.
It was the Unit, not Kathryn and Kit, who drilled the pilot hole through each Eddorian's hard-held block and enlarged it into a working orifice.
He wrapped the other end of the leather thong securely around the remaining end of the Alder branch, and then looped the thong once around the stick he used to burn the pilot hole.