Austrodrillia dimidiata is a species of sea snail, a marine gastropod mollusk in the family Horaiclavidae.

(Description by Joseph Verco) The solid, elongate-fusiform shell consists of 6+1⁄2 whorls, including the blunt protoconch, which merges into the spire insensibly.

The first whorl and a half are smooth and rather flat; the next is scarcely convex, and has at first distant invalid axial angulations, which gradually become more numerous and costulate.

The spire-whorls are subconvex, subangulate just below the middle, and have the upper fourth somewhat adpressed just below the simple impressed suture.

The outer lip is solid but sharp, with a deep round sinus separated from the ascending suture by a callus from the posterior part of the inner lip, then straightly convexly antecurrent to two shallower sinuses at the base of the siphonal canal.