irritate

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To rouse to impatience or anger; annoy: a loud bossy voice that irritates listeners. See Synonyms at annoy.
2. v. To chafe or inflame.
3. v. Physiology To cause physiological activity or response in (an organ or tissue), as by application of a stimulus.
4. v. To be a cause of impatience or anger.

Century Dictionary and Cyclopedia

1. To render null and void.
2. Excited; exasperated; intensified.
3. To excite to resentment or anger; annoy; vex; exasperate: as, to be irritated by an officious or a tedious person.
4. To excite to automatic action by external agency, as organic tissue; produce motion, contraction, or inflammation in by stimulation: as, to irritate the skin by chafing or the nerves by teasing.
5. To give greater force or energy to; excite.
6. Synonyms Provoke, Incense, etc. (see exasperate); fret, chafe, nettle, sting, annoy, gall, inflame, excite, anger, enrage.

Wiktionary

1. v. To provoke impatience, anger, or displeasure.
2. v. To introduce irritability.
3. v. To cause or induce displeasure or irritation.
4. v. To induce pain in (all or part of a body or organism).

GNU Webster's 1913

1. adj. Excited; heightened.
2. v. To increase the action or violence of; to heighten excitement in; to intensify; to stimulate.
3. v. To excite anger or displeasure in; to provoke; to tease; to exasperate; to annoy; to vex.
4. v. To produce irritation in; to stimulate; to cause to contract. See Irritation, n., 2.
5. v. To make morbidly excitable, or oversensitive; to fret
6. v. To render null and void.

WordNet 3.0

1. v. excite to some characteristic action or condition, such as motion, contraction, or nervous impulse, by the application of a stimulus
2. v. excite to an abnormal condition, or chafe or inflame
3. v. cause annoyance in; disturb, especially by minor irritations