To perforate with a trephine.
To use a trephine during surgery.
A surgical instrument with a cylindrical blade used to remove a circular section of tissue, f.e. bone or cornea; a trepan.
To dig underneath (something), to make a passage for destructive or military purposes; to sap.
To weaken or work against; to hinder, sabotage.
To erode the base or foundation of something, e.g. by the action of water.