What is "trepans"

Usage examples of "trepans".

Shep's one-eyed stare, as direct a moment of contact as ever he'd made with his brother, was an image suitable for any horror-movie poster: the essence of terror, the look of the victim just before the alien from another world rips his throat open, just before the zombie tears his heart out, just before the lunatic psychiatrist trepans his skull and devours his brain with a good Cabernet.

This month's exhibit was on the history of surgical instruments, and I glanced at the array of therapeutic weaponry - from crude, stone trepans exposing the cerebral tissue within a mannikin's skull to lasers traversing arterial tunnels.