entasis, in architecture, the convex curve given to a column, spire, or similar upright member, in an attempt to correct the optical illusion of hollowness or weakness that would arise from normal tapering. Entasis is almost universal in Classical columns. Exaggerated in Greek archaic Doric work, it grew more and more subtle in the 5th and 4th centuries bc. Entasis is also occasionally found in Gothic spires and in the smaller Romanesque columns.