Source : Webster's Revised Unabridged Dictionary (1913)

Quack grass \Quack" grass`\ (Bot.)
   See {Quitch grass}.

Source : WordNet®

quack grass
     n : European grass spreading rapidly by creeping rhizomes;
         naturalized in North America as a weed [syn: {dog grass},
          {couch grass}, {quackgrass}, {quick grass}, {witch grass},
          {witchgrass}, {Agropyron repens}]