Spirotropis phaeacra is a species of sea snail, a marine gastropod mollusk in the family Drilliidae.

(Original description) The conical, angulated, tubercled shell is thin, polished, glassy, with a blunt, dun apex, a contracted base, and a longish columella.

Toward the bottom of each whorl is a row of about twelve round, blunt-tipped, rather prominent tubercles, which form an angulated keel where otherwise there is no carination.

The shell contains 6 short whorls of slow growth, with a longish, drooping, somewhat concave shoulder, angulated below the middle by the row of tubercles, and slightly contracted into the inferior suture.

The outer lip is thin, with a pretty regular convex curve, which is flattened at the summit, and prolonged in a straightish line at the siphonal canal.