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noun knot·grass \ˈnät-ˌgras\

Definition of knotgrass

  1. 1 :  a cosmopolitan prostrate weed (Polygonum aviculare) of the buckwheat family with jointed stems, prominent sheathing stipules, and minute flowers; broadly :  any of several congeneric plants

  2. 2 :  any of several grasses (as Paspalum distichum) with markedly jointed stems

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