Meaning of skewback

skew•back

Pronunciation: (sky'bak"), [key]
— n. Archit.
  1. a sloping surface against which the end of an arch rests.
  2. a stone, course of masonry, or the like, presenting such a surface.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.