Knefastia glypta is an extinct species of sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, the turrids and allies.

The sculpture is modified on the later volutions by the increasing prominence of the peripheral spiral and that directly behind it, the intercalation of secondaries, and the development of undulatory axials 8 to 10 to the whorl.

The periphery of antepenult whorls is situated a little more than one third of the distance across from the anterior to the posterior suture, outlined by a simple elevated spiral cord.

A second spiral of similar character and almost equal elevation is a short distance behind it, the two separated from one another by a shallow interspace in which a medial secondary and two microscopically fine tertiaries are symmetrically intercalated.

The outer lip is widely flaring incrementally, narrowly but deeply sinuated in front of the anterior primary, distantly lirated within.