The Collaborative International Dictionary of English v.0.48:

Rush \Rush\, n. [OE. rusche, rische, resche, AS. risce, akin to
   LG. rusk, risch, D. & G. rusch; all probably fr. L. ruscum
   butcher's broom; akin to Goth. raus reed, G. rohr.]
   1. (Bot.) A name given to many aquatic or marsh-growing
      endogenous plants with soft, slender stems, as the species
      of Juncus and Scirpus.
      [1913 Webster]

   Note: Some species are used in bottoming chairs and plaiting
         mats, and the pith is used in some places for wicks to
         lamps and rushlights.
         [1913 Webster]

   2. The merest trifle; a straw.
      [1913 Webster]

            John Bull's friendship is not worth a rush.
                                                  --Arbuthnot.
      [1913 Webster]

   Bog rush. See under Bog.

   Club rush, any rush of the genus Scirpus.

   Flowering rush. See under Flowering.

   Nut rush
      (a) Any plant of the genus Scleria, rushlike plants with
          hard nutlike fruits.
      (b) A name for several species of Cyperus having
          tuberous roots.

   Rush broom, an Australian leguminous plant (Viminaria
      denudata), having long, slender branches. Also, the
      Spanish broom. See under Spanish.

   Rush candle, See under Candle.

   Rush grass, any grass of the genus Vilfa, grasses with
      wiry stems and one-flowered spikelets.

   Rush toad (Zool.), the natterjack.

   Scouring rush. (Bot.) Same as Dutch rush, under Dutch.


   Spike rush, any rushlike plant of the genus Eleocharis,
      in which the flowers grow in dense spikes.

   Sweet rush, a sweet-scented grass of Arabia, etc.
      (Andropogon schoenanthus), used in Oriental medical
      practice.

   Wood rush, any plant of the genus Luzula, which differs
      in some technical characters from Juncus.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spike \Spike\, n. [Akin to LG. spiker, spieker, a large nail, D.
   spijker, Sw. spik, Dan. spiger, Icel. sp[imac]k; all perhaps
   from L. spica a point, an ear of grain; but in the sense of
   nail more likely akin to E. spoke of a wheel. Cf. Spine.]
   1. A sort of very large nail; also, a piece of pointed iron
      set with points upward or outward.
      [1913 Webster]

   2. Anything resembling such a nail in shape.
      [1913 Webster]

            He wears on his head the corona radiata . . .; the
            spikes that shoot out represent the rays of the sun.
                                                  --Addison.
      [1913 Webster]

   3. An ear of corn or grain.
      [1913 Webster]

   4. (Bot.) A kind of flower cluster in which sessile flowers
      are arranged on an unbranched elongated axis.
      [1913 Webster]

   Spike grass (Bot.), either of two tall perennial American
      grasses (Uniola paniculata, and Uniola latifolia)
      having broad leaves and large flattened spikelets.

   Spike rush. (Bot.) See under Rush.

   Spike shell (Zool.), any pteropod of the genus Styliola
      having a slender conical shell.

   Spike team, three horses, or a horse and a yoke of oxen,
      harnessed together, a horse leading the oxen or the span.
      [U.S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

spike rush
    n 1: a sedge of the genus Eleocharis