What is "gemel window"

Gemel \Gem"el\, n.

1. One of the twins. [Obs.]
   --Wyclif.

2. (Heb.) One of the barrulets placed parallel and closed to each other. Cf. Bars gemel, under Gemel,

   1. Two gemels silver between two griffins passant.
      --Strype.

      Gemel hinge (Locksmithing), a hinge consisting of an eye or loop and a hook.

      Gemel ring, a ring with two or more links; a gimbal. See Gimbal.

      Gemel window, a window with two bays.