n. & v.
n. 1 a cylindrical saw formerly used by surgeons for removing part of the bone of the skull. 2 a borer for sinking shafts.
v.tr. (trepanned, trepanning) perforate (the skull) with a trepan. trepanation n. trepanning n.
[ ME f. med.L trepanum f. Gk trupanon f. trupao bore f. trupe hole ]