entasis

/หˆษ›ntษ™sษชs/

IPA: /EH1 N T AH0 S IH0 S/

noun
  1. 1

    A slight convex curvature introduced into the shaft of a column for aesthetic reasons, or to compensate for the illusion of concavity.

Source: https://en.wiktionary.org/wiki/entasis