Ir`ri*ta"tion (?), n. [L.
irritatio: cf. F. irritation.]
1. The act of irritating, or exciting, or the
state of being irritated; excitement; stimulation, usually of an
undue and uncomfortable kind; especially, excitement of anger or
passion; provocation; annoyance; anger.
The whole body of the arts and sciences composes one
vast machinery for the irritation and development of the human
intellect.
De Quincey.
2. (Physiol.) The act of exciting, or
the condition of being excited to action, by stimulation; -- as, the
condition of an organ of sense, when its nerve is affected by some
external body; esp., the act of exciting muscle fibers to
contraction, by artificial stimulation; as, the irritation of
a motor nerve by electricity; also, the condition of a muscle and
nerve, under such stimulation.
3. (Med.) A condition of morbid
excitability or oversensitiveness of an organ or part of the body; a
state in which the application of ordinary stimuli produces pain or
excessive or vitiated action.