The Collaborative International Dictionary of English v.0.48:

Anta \An"ta\, n.; pl. Ant[ae]. [L.] (Arch.)
   A species of pier produced by thickening a wall at its
   termination, treated architecturally as a pilaster, with
   capital and base.
   [1913 Webster]

   Note: Porches, when columns stand between two ant[ae], are
         called in Latin in antis.
         [1913 Webster] antiacid