The Collaborative International Dictionary of English v.0.48:

Bristle \Bris"tle\, v. i.
   1. To rise or stand erect, like bristles.
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            His hair did bristle upon his head.   --Sir W.
                                                  Scott.
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   2. To appear as if covered with bristles; to have standing,
      thick and erect, like bristles.
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            The hill of La Haye Sainte bristling with ten
            thousand bayonets.                    --Thackeray.
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            Ports bristling with thousands of masts. --Macaulay.
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   3. To show defiance or indignation.
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   To bristle up, to show anger or defiance.
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The Collaborative International Dictionary of English v.0.48:

Bristle \Bris"tle\ (br[i^]s"s'l), n. [OE. bristel, brustel, AS.
   bristl, byrst; akin to D. borstel, OHG. burst, G. borste,
   Icel. burst, Sw. borst, and to Skr. bh[.r]shti edge, point,
   and prob, L. fastigium extremity, Gr. 'a`flaston stern of a
   ship, and E. brush, burr, perh. to brad. [root]96.]
   1. A short, stiff, coarse hair, as on the back of swine.
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   2. (Bot.) A stiff, sharp, roundish hair. --Gray.
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The Collaborative International Dictionary of English v.0.48:

Bristle \Bris"tle\, v. t. [imp. & p. p. Bristled; p. pr. & vb.
   n. Bristling.]
   1. To erect the bristles of; to cause to stand up, as the
      bristles of an angry hog; -- sometimes with up.
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            Now for the bare-picked bone of majesty
            Doth dogged war bristle his angry crest. --Shak.
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            Boy, bristle thy courage up.          --Shak.
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   2. To fix a bristle to; as, to bristle a thread.
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WordNet (r) 3.0 (2006):

bristle
    n 1: a stiff fiber (coarse hair or filament); natural or
         synthetic
    2: a stiff hair
    v 1: be in a state of movement or action; "The room abounded
         with screaming children"; "The garden bristled with
         toddlers" [syn: abound, burst, bristle]
    2: rise up as in fear; "The dog's fur bristled"; "It was a sight
       to make one's hair uprise!" [syn: bristle, uprise, stand
       up]
    3: have or be thickly covered with or as if with bristles;
       "bristling leaves"
    4: react in an offended or angry manner; "He bristled at her
       suggestion that he should teach her how to use the program"