Definition of trepan

• n. - A crown-saw or cylindrical saw for perforating the skull, turned, when used, like a bit or gimlet. See Trephine.
• n. - A kind of broad chisel for sinking shafts.
• v. t. & i. - To perforate (the skull) with a trepan, so as to remove a portion of the bone, and thus relieve the brain from pressure or irritation; to perform an operation with the trepan.
• n. - A snare; a trapan.
• n. - a deceiver; a cheat.
• v. t. - To insnare; to trap; to trapan.