Merriam-Webster Collegiate Dictionary - itch

 I. verb  Etymology: Middle English icchen, from Old English giccan; akin to Old High German jucchen to ~  Date: before 12th century  intransitive verb  1.  a. to have an ~ her arm ~ed  b. to produce an ~y sensation long underwear that ~es  2. to have a restless desire or hankering for something were ~ing to go outside  transitive verb  1. to cause to ~  2. vex, irritate  II. noun  Date: before 12th century  1.  a. an uneasy irritating sensation in the upper surface of the skin usually held to result from mild stimulation of pain receptors  b. a skin disorder accompanied by such a sensation; especially a contagious eruption caused by a mite (Sarcoptes scabiei) that burrows in the skin and causes intense ~ing  2.  a. a restless usually constant often compulsive desire an ~ to travel  b. lust, prurience  • ~iness noun  • ~y adjective