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.
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   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.
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   2. The merest trifle; a straw.
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            John Bull's friendship is not worth a rush.
                                                  --Arbuthnot.
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   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.
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The Collaborative International Dictionary of English v.0.48:

bog \bog\ (b[o^]g), n. [Ir. & Gael. bog soft, tender, moist: cf.
   Ir. bogach bog, moor, marsh, Gael. bogan quagmire.]
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   1. A quagmire filled with decayed moss and other vegetable
      matter; wet spongy ground where a heavy body is apt to
      sink; a marsh; a morass.
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            Appalled with thoughts of bog, or caverned pit,
            Of treacherous earth, subsiding where they tread.
                                                  --R. Jago.
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   2. A little elevated spot or clump of earth, roots, and
      grass, in a marsh or swamp. [Local, U. S.]
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   Bog bean. See Buck bean.

   Bog bumper (bump, to make a loud noise), Bog blitter,
   Bog bluiter, Bog jumper, the bittern. [Prov.]

   Bog butter, a hydrocarbon of butterlike consistence found
      in the peat bogs of Ireland.

   Bog earth (Min.), a soil composed for the most part of
      silex and partially decomposed vegetable fiber. --P. Cyc.

   Bog moss. (Bot.) Same as Sphagnum.

   Bog myrtle (Bot.), the sweet gale.

   Bog ore. (Min.)
      (a) An ore of iron found in boggy or swampy land; a
          variety of brown iron ore, or limonite.
      (b) Bog manganese, the hydrated peroxide of manganese.

   Bog rush (Bot.), any rush growing in bogs; saw grass.

   Bog spavin. See under Spavin.
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