Source : Webster's Revised Unabridged Dictionary (1913)

Relais \Re*lais"\ (re*l[asl]"), n. [F. See {Relay}, n.] (Fort.)
   A narrow space between the foot of the rampart and the scarp
   of the ditch, serving to receive the earth that may crumble
   off or be washed down, and prevent its falling into the
   ditch. --Wilhelm.