The Collaborative International Dictionary of English v.0.48:

Nettle \Net"tle\, n. [AS. netele; akin to D. netel, G. nessel,
   OHG. nezz["i]la, nazza, Dan. nelde, n[aum]lde, Sw.
   n[aum]ssla; cf, Lith. notere.] (Bot.)
   A plant of the genus Urtica, covered with minute sharp
   hairs containing a poison that produces a stinging sensation.
   Urtica gracilis is common in the Northern, and Urtica
   chamaedryoides in the Southern, United States. The common
   European species, Urtica urens and Urtica dioica, are
   also found in the Eastern united States. Urtica pilulifera
   is the Roman nettle of England.
   [1913 Webster]

   Note: The term nettle has been given to many plants related
         to, or to some way resembling, the true nettle; as:

   Australian nettle, a stinging tree or shrub of the genus
      Laportea (as Laportea gigas and Laportea moroides);
      -- also called nettle tree.

   Bee nettle, Hemp nettle, a species of Galeopsis. See
      under Hemp.

   Blind nettle, Dead nettle, a harmless species of
      Lamium.

   False nettle (Baehmeria cylindrica), a plant common in
      the United States, and related to the true nettles.

   Hedge nettle, a species of Stachys. See under Hedge.

   Horse nettle (Solanum Carolinense). See under Horse.

   nettle tree.
   (a) Same as Hackberry.
   (b) See Australian nettle (above).

   Spurge nettle, a stinging American herb of the Spurge
      family (Jatropha urens).

   Wood nettle, a plant (Laportea Canadensis) which stings
      severely, and is related to the true nettles.
      [1913 Webster]

   Nettle cloth, a kind of thick cotton stuff, japanned, and
      used as a substitute for leather for various purposes.

   Nettle rash (Med.), an eruptive disease resembling the
      effects of whipping with nettles.

   Sea nettle (Zool.), a medusa.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nettle \Net"tle\, v. t. [imp. & p. p. Nettled; p. pr. & vb. n.
   Nettling.]
   To fret or sting; to irritate or vex; to cause to experience
   sensations of displeasure or uneasiness not amounting to
   violent anger.
   [1913 Webster]

         The princes were so nettled at the scandal of this
         affront, that every man took it to himself.
                                                  --L'Estrange.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nettle
    n 1: any of numerous plants having stinging hairs that cause
         skin irritation on contact (especially of the genus Urtica
         or family Urticaceae)
    v 1: sting with or as with nettles and cause a stinging pain or
         sensation [syn: nettle, urticate]
    2: cause annoyance in; disturb, especially by minor irritations;
       "Mosquitoes buzzing in my ear really bothers me"; "It
       irritates me that she never closes the door after she leaves"
       [syn: annoy, rag, get to, bother, get at,
       irritate, rile, nark, nettle, gravel, vex,
       chafe, devil]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "nettle":
   aggravate, agitate, annoy, arouse, badger, bait, be at, bedevil,
   beset, blow the coals, bother, bramble, brier, bristle, brown off,
   bug, bullyrag, burn up, burr, cactus, catchweed, chafe, chivy,
   cleavers, devil, discompose, distemper, disturb, dog, embitter,
   exasperate, excite, exercise, fan, fan the flame, fash,
   feed the fire, ferment, fire, foment, fret, get, goose grass,
   gripe, harass, harry, heat, heat up, heckle, hector, hound, huff,
   impassion, incense, incite, inflame, instigate, irk, irritate,
   miff, molest, nag, needle, nudzh, peeve, persecute, perturb,
   pester, pick on, pine needle, pique, plague, plaque,
   pluck the beard, pother, prickle, provoke, put out, put up to,
   quill, rally, rankle, ride, rile, roil, ruffle, set on, set up,
   sic on, spicule, spiculum, spike, spikelet, spine, sticker,
   stir the blood, stir the embers, stir up, tease, thistle, thorn,
   tickle, torment, try the patience, tweak the nose, upset, vex,
   whet, whip up, work up, worry, yucca



Easton's 1897 Bible Dictionary:

Nettle
   (1.) Heb. haral, "pricking" or "burning," Prov. 24:30, 31 (R.V.
   marg., "wild vetches"); Job 30:7; Zeph. 2:9. Many have supposed
   that some thorny or prickly plant is intended by this word, such
   as the bramble, the thistle, the wild plum, the cactus or
   prickly pear, etc. It may probably be a species of mustard, the
   Sinapis arvensis, which is a pernicious weed abounding in
   corn-fields. Tristram thinks that this word "designates the
   prickly acanthus (Acanthus spinosus), a very common and
   troublesome weed in the plains of Palestine."

     (2.) Heb. qimmosh, Isa. 34:13; Hos. 9:6; Prov. 24:31 (in both
   versions, "thorns"). This word has been regarded as denoting
   thorns, thistles, wild camomile; but probably it is correctly
   rendered "nettle," the Urtica pilulifera, "a tall and vigorous
   plant, often 6 feet high, the sting of which is much more severe
   and irritating than that of our common nettle."