Ab'ap-tis'ta or Ab'ap-tis'ton, n.

n. [Gr. ἀβάπτιστον (sc. τρύπανον) from a priv. and βαπτίζειν, to dip into; L. Lat. abaptistum.] (Surg.) The old trephine or trepan, a saw whose conical shape prevented it from plunging into the brain. Dunglison.