The Collaborative International Dictionary of English v.0.48:

Epaule \E*paule"\, n. [F. ['e]paule shoulder, shoulder of a
   bastion. See Epaulet, and cf. Spall the shoulder.]
   (Fort.)
   The shoulder of a bastion, or the place where its face and
   flank meet and form the angle, called the angle of the
   shoulder.
   [1913 Webster]