(n)a slight convexity in the shaft of a column; compensates for the illusion of concavity that viewers experience when the sides are perfectly straight
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
‖n. [ NL., from Gr. &unr_; a stretching; fr. &unr_;; &unr_; in + &unr_; to extend. ] 1. (Arch.) A slight convex swelling of the shaft of a column. [ 1913 Webster ]