Entasis is a term used in architecture for a slight convex curvature or swelling in the shaft of a column. It is designed to counteract the optical illusion that the column appears to be tapering towards the top, creating an impression of weakness. There are several synonyms for entasis, such as bulging, swelling, curve, and convexity. Additionally, other words such as expansion, broadening, and enlargement can also be used to describe the same concept. The use of synonyms helps to more clearly and accurately convey the intended meaning, especially when discussing complex architectural structures.