TREPAN', noun [Latin tero, terebra, on the root Rp.] In surgery, a circular saw for perforating the skull. It resembles a wimble. TREPAN', verb transitive To perforate the skull and take out a piece; a surgical operation for relieving the brain from pressure or irritation. TREPAN, a snare, and trepan to ensnare, are from trap, and written trepan which see.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI