The Collaborative International Dictionary of English v.0.48:

Itch \Itch\ ([i^]ch), v. i. [imp. & p. p. Itched ([i^]cht); p.
   pr. & vb. n. Itching.] [OE. icchen, [yogh]icchen, AS.
   giccan; akin to D. jeuken, joken, G. jucken, OHG. jucchen.]
   [1913 Webster]
   1. To have an uneasy sensation in the skin, which inclines
      the person to scratch the part affected.
      [1913 Webster]

            My mouth hath itched all this long day. --Chaucer.
      [1913 Webster]

   2. To have a constant desire or teasing uneasiness; to long
      for; as, itching ears. "An itching palm." --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

itching
    n 1: an irritating cutaneous sensation that produces a desire to
         scratch [syn: itch, itchiness, itching]

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "itching":
   abscess, aching for, ague, an universal wolf, anemia, ankylosis,
   anoxia, apnea, appetence, appetency, appetite, appetition,
   asphyxiation, asthma, ataxia, athirst, atrophy, backache, bent on,
   bleeding, blennorhea, cachexia, cachexy, chill, chills, colic,
   concupiscent, constipation, consumed with desire, convulsion,
   coughing, coveting, craving, crazy to, cyanosis, desirous of,
   devoured by desire, diarrhea, dizziness, dropsy, dying for,
   dying to, dysentery, dyspepsia, dyspnea, edema, ejaculatory,
   emaciation, fain of, fainting, fatigue, fervid, fever,
   fibrillation, flux, fond of, goatish, growth, hemorrhage,
   high blood pressure, horny, hot, hot-blooded, hunger, hungering,
   hungry, hydrops, hypertension, hypotension, icterus,
   inclined toward, indigestion, inflammation, insomnia, itch,
   itchiness, itching for, itchy, jaundice, keen on,
   labored breathing, lascivious, leaning toward, libidinous,
   lickerish, low blood pressure, lumbago, lustful, mad on,
   mad with lust, mania, marasmus, nasal discharge, nausea, necrosis,
   orgasmic, orgastic, pain, paralysis, partial to, passionate,
   prurience, pruriency, prurient, pruritus, randy, rash, rheum,
   salacious, sclerosis, seizure, set on, sex-starved, sexual desire,
   sexy, shock, skin eruption, sneezing, sore, spasm, spoiling for,
   steamy, tabes, tachycardia, thirst, thirsting, thirsty, tumor,
   unsatisfied, upset stomach, vertigo, vomiting, wasting, wild to,
   yeuk