The Collaborative International Dictionary of English v.0.48:

Quadrat \Quad"rat\, n. [F. quadrat, cadrat. See Quadrate.]
   1. (Print.) A block of type metal lower than the letters, --
      used in spacing and in blank lines. [Abbrev. quad.]
      [1913 Webster]

   2. An old instrument used for taking altitudes; -- called
      also geometrical square, and line of shadows.
      [1913 Webster]