Slight swelling in depiction of the shaft of a column, it was invented by the ancient Greeks to overcome the illusion of concavity when parallel-sided or regularly tapered columns were used together. Source: Julia M Ehresmann, "The Pocket Dictionary of Art Terms"<br><br>An almost imperceptible convex tapering (an apparent swelling) in the shaft of a column.(pr. en-TAH-s&#601;s)