Source : Webster's Revised Unabridged Dictionary (1913)

Crossette \Cros*sette"\ (kr?s-s?t`), n. [F., dim. of crosse. See
   {Crosier}.] (Arch.)
   (a) A return in one of the corners of the architrave of a
       door or window; -- called also {ancon}, {ear}, {elbow}.
   (b) The shoulder of a joggled keystone.