The Collaborative International Dictionary of English v.0.48:

irritated \irritated\ adj.
   aroused to impatience or anger; as, made an irritated
   gesture.

   Syn: annoyed, nettled, peeved, pissed, stung.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Irritate \Ir"ri*tate\, v. t. [imp. & p. p. Irritated; p. pr. &
   vb. n. Irritating.] [L. irritatus, p. p. of irritare. Of
   doubtful origin.]
   [1913 Webster]
   1. To increase the action or violence of; to heighten
      excitement in; to intensify; to stimulate.
      [1913 Webster]

            Cold maketh the spirits vigorous and irritateth
            them.                                 --Bacon.
      [1913 Webster]

   2. To excite anger or displeasure in; to provoke; to tease;
      to exasperate; to annoy; to vex; as, the insolence of a
      tyrant irritates his subjects.
      [1913 Webster]

            Dismiss the man, nor irritate the god:
            Prevent the rage of him who reigns above. --Pope.
      [1913 Webster]

   3. (Physiol.) To produce irritation in; to stimulate; to
      cause to contract. See Irritation, n., 2.
      [1913 Webster]

   4. (Med.) To make morbidly excitable, or oversensitive; to
      fret; as, the skin is irritated by friction; to irritate a
      wound by a coarse bandage.

   Syn: To fret; inflame; excite; provoke; tease; vex;
        exasperate; anger; incense; enrage.

   Usage: To Irritate, Provoke, Exasperate. These words
          express different stages of excited or angry feeling.
          Irritate denotes an excitement of quick and slightly
          angry feeling which is only momentary; as, irritated
          by a hasty remark. To provoke implies the awakening of
          some open expression of decided anger; as, a provoking
          insult. Exasperate denotes a provoking of anger at
          something unendurable. Whatever comes across our
          feelings irritates; whatever excites anger provokes;
          whatever raises anger to a high point exasperates.
          "Susceptible and nervous people are most easily
          irritated; proud people are quickly provoked; hot and
          fiery people are soonest exasperated." --Crabb.
          [1913 Webster]

WordNet (r) 3.0 (2006):

irritated
    adj 1: aroused to impatience or anger; "made an irritated
           gesture"; "feeling nettled from the constant teasing";
           "peeved about being left out"; "felt really pissed at her
           snootiness"; "riled no end by his lies"; "roiled by the
           delay" [syn: annoyed, irritated, miffed, nettled,
           peeved, pissed, pissed off, riled, roiled,
           steamed, stung]