• WordNet 3.6
    • n knotgrass low-growing weedy grass with spikelets along the leaf stems
    • ***
Webster's Revised Unabridged Dictionary
    • n Knotgrass (Bot) a common weed with jointed stems Polygonum aviculare; knotweed.☞ An infusion of Polygonum aviculare was once supposed to have the effect of stopping the growth of an animal, and hence it was called, as by Shakespeare, “hindering knotgrass.” "We want a boy extremely for this function,
      Kept under for a year with milk and knotgrass ."
    • ***
Century Dictionary and Cyclopedia
    • n knotgrass A weed of almost world-wide distribution, Polygonum aviculare: so called from the numerous nodes in its stems and its thickly spreading habit. It is a tough trailing and branching plant, common in trodden ground, and often carpeting dooryards, etc. (Also called knotweed, goose-grass, cow-grass, doorweed, etc.) An infusion of it was formerly supposed to retard bodily growth, whence Shakspere calls it “hindering knot-grass.”
    • n knotgrass By extension, any plant of the genus Polygonum, properly knotweed.
    • n knotgrass In occasional use, a plant of some other genus more or less similar. Any of the species of Illecebrum or Paronychia; a whitlow-wort, A variety of the false oat, Arrhenatherum avenaceum, having a knotty rootstock. [Prov. Eng.] The florin-grass, Agrostis vulgaris, var. alba (stolonifera). [Prov Eng.] This may be the plant mentioned by Milton.
    • n knotgrass Couch-grass: a use of doubtful appropriateness.
    • ***


In literature:

The hedgehog footed through the knotgrass slowly, grubbing with his snout to right and left of him.
""Wee Tim'rous Beasties"" by Douglas English
Knotgrass, hinders growth, 225.
"Folk-lore of Shakespeare" by Thomas Firminger Thiselton-Dyer
Grim had then to go where flags and knotgrass pricked tiny, almost invisible holes in the ice.
"Grim: The Story of a Pike" by Svend Fleuron