Source : Webster's Revised Unabridged Dictionary (1913)

Flanch \Flanch\, n.; pl. {Flanches}. [Prov. E., a projection,
   OF. flanche flank. See {Flank}.]
   1. A flange. [R.]. (Her.) A bearing consisting of a segment
      of a circle encroaching on the field from the side.

   Note: Flanches are always in pairs. A pair of flanches is
         considered one of the subordinaries.