[1] : The Collaborative International Dictionary of English v.0.48

thorn \thorn\, n. as. thornorn; akin to os.  ofries. thorn,
   d. doorn, g. dorn, dan. torn, sw. t"orne, icel. thornorn,
   goth. thorna'urnus; cf. pol. tarn, russ. tern' the
   blackthorn, ternie thorns, skr. t.r.na grass, blade of
   grass. root53.
   1. a hard and sharp-pointed projection from a woody stem;
      usually, a branch so transformed; a spine.
      1913 webster

   2. bot. any shrub or small tree which bears thorns;
      especially, any species of the genus crataegus, as the
      hawthorn, whitethorn, cockspur thorn.
      1913 webster

   3. fig.: that which pricks or annoys as a thorn; anything
      troublesome; trouble; care.
      1913 webster

            there was given to me a thorn in the flesh, the
            messenger of satan to buffet me.      --2 cor. xii.
                                                  7.
      1913 webster

            the guilt of empire, all its thorns and cares,
            be only mine.                         --southern.
      1913 webster

   4. the name of the anglo-saxon letter ?, capital form ?. it
      was used to represent both of the sounds of english th, as
      in thin, then. so called because it was the initial letter
      of thorn, a spine.
      1913 webster

   thorn apple bot., jamestown weed.

   thorn broom bot., a shrub that produces thorns.

   thorn hedge, a hedge of thorn-bearing trees or bushes.

   thorn devil. zool. see moloch, 2.

   thorn hopper zool., a tree hopper thelia crataegi
      which lives on the thorn bush, apple tree, and allied
      trees.
      1913 webster
see also:
thorn apple thorn broom thorn hedge thorn devil moloch thorn hopper 
thelia crataegi 

[2] : The Collaborative International Dictionary of English v.0.48

thorn \thorn\, v. t.
   to prick, as with a thorn. poetic
   1913 webster

         i am the only rose of all the stock
         that never thorn'd him.                  --tennyson.
   1913 webster

[3] : WordNet (r) 2.0

thorn
     n 1: something that causes irritation and annoyance; "he's a
          thorn in my flesh" syn: irritant
     2: a sharp-pointed tip on a stem or leaf syn: spine, prickle,
         pricker, sticker
     3: a germanic character of runic origin
see also:
irritant spine prickle pricker sticker 

[4] : Moby Thesaurus II by Grady Ward, 1.0

93 moby thesaurus words for "thorn":
   adherent, adhesive, affliction, annoyance, bane, barb, barnacle,
   bitter cup, bitter draft, bitter draught, bitter pill, bother,
   bramble, brier, bristle, bugbear, bulldog, burden, burden of care,
   burr, cactus, calamity, cankerworm of care, care, catchweed,
   cement, cleavers, cross, crown of thorns, crushing burden, curse,
   death, decal, decalcomania, destruction, disease, distress,
   encumbrance, evil, gall, gall and wormwood, glue, goose grass,
   grievance, gunk, harm, infliction, irritant, irritation, leech,
   limpet, load, molasses, mucilage, needle, nemesis, nettle,
   nuisance, open wound, oppression, pack of troubles, paste,
   peck of troubles, pest, pestilence, pine needle, plague, plaster,
   point, prickle, quill, remora, running sore, scourge,
   sea of troubles, sorrow, spicule, spiculum, spike, spikelet, spine,
   sticker, syrup, thistle, torment, torture, trouble, vexation,
   visitation, waters of bitterness, weight, woe, yucca

[5] : Easton's 1897 Bible Dictionary

thorn
   1. heb. hedek prov. 15:19, rendered "brier" in micah 7:4.
   some thorny plant, of the solanum family, suitable for hedges.
   this is probably the so-called "apple of sodom," which grows
   very abundantly in the jordan valley. "it is a shrubby plant,
   from 3 to 5 feet high, with very branching stems, thickly clad
   with spines, like those of the english brier, with leaves very
   large and woolly on the under side, and thorny on the midriff."
   
     2. heb. kotz gen. 3:18; hos. 10:8, rendered _akantha_ by
   the lxx. in the new testament this word _akantha_ is also
   rendered "thorns" matt. 7:16; 13:7; heb. 6:8. the word seems
   to denote any thorny or prickly plant jer. 12:13. it has been
   identified with the ononis spinosa by some.
   
     3. heb. na'atzutz isa. 7:19; 55:13. this word has been
   interpreted as denoting the zizyphus spina christi, or the
   jujube-tree. it is supposed by some that the crown of thorns
   placed in wanton cruelty by the roman soldiers on our saviour's
   brow before his crucifixion was plaited of branches of this
   tree. it overruns a great part of the jordan valley. it is
   sometimes called the lotus-tree. "the thorns are long and sharp
   and recurved, and often create a festering wound." it often
   grows to a great size. see crown of thorns.
   
     4. heb. atad ps. 58:9 is rendered in the lxx. and vulgate
   by rhamnus, or lycium europoeum, a thorny shrub, which is common
   all over palestine. from its resemblance to the box it is
   frequently called the box-thorn.
   
see also:
thorns 

Thorn >> T Words
Thorn, definition of term: Thorn
thorn_pag1.html

Thorn Devil >> T Words
Thorn Devil, definition of term: Thorn Devil
thorn+devil_pag1.html

Thorn Apple >> T Words
Thorn Apple, definition of term: Thorn Apple
thorn+apple_pag1.html