from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A trepan having a conical shape so that injurious penetration of the brain is impossible.
from The Century Dictionary and Cyclopedia
- n. In surgery, an old form of trepan, the crown of which was made conical, or provided with a ring, collar, or other contrivance, to prevent it from penetrating the cranium too far.
From Ancient Greek ἀβάπτιστος (abaptistos, "not dipped"). (Wiktionary)