Source : Webster's Revised Unabridged Dictionary (1913)

Quad \Quad\, Quade \Quade\, a. [Akin to AS. cw[=ae]d, cwead,
   dung, evil, G. kot, dung, OHG. qu[=a]t.]
   Evil; bad; baffling; as, a quade wind. [Obs.]

         Sooth play, quad play, as the Fleming saith. --Chaucer.

Quad \Quad\, n. (Print.)
   A quadrat.

Quad \Quad\, n. (Arch.)
   A quadrangle; hence, a prison. [Cant or Slang]

Source : WordNet®

quad
     n 1: one of four children born at the same time from the same
          pregnancy [syn: {quadruplet}]
     2: a muscle of the thigh that extends the leg [syn: {quadriceps},
         {quadriceps femoris}, {musculus quadriceps femoris}]
     3: (printing) a block of type without a raised letter; used for
        spacing between words [syn: {space}]
     4: a rectangular area surrounded on all sides by buildings
        [syn: {quadrangle}]

Source : Free On-Line Dictionary of Computing

quad
     
        1. Two bits; synonym for {quarter}, {crumb}, {tayste}.
     
        2. A four-pack of anything (compare {hex}).
     
        3. The rectangle or box glyph used in the APL language for
        various arcane purposes mostly related to I/O.
     
        Former Ivy-Leaguers and Oxford types are said to associate it
        with nostalgic memories of dear old University (short for
        "quadrangle").
     
        [{Jargon File}]