A low-grade but sharp, prickling displeasure provoked by something bothersome.
A low-grade but sharp, prickling displeasure provoked by something bothersome — often by persistent or repeated provocation.
Like annoyance in intensity, but typically hotter and more abrasive — the emotional equivalent of a rubbed-raw spot (the word's parallel physical sense is “chafing, inflammation”), and more about the internal state of being provoked than about naming the source. Milder and more diffuse than frustration (no blocked goal needed), less literary than vexation, and well short of exasperation, indignation, or the high-band anger words. Unlike pique, it has no wounded-pride component.
Early 15c., originally in physiology (of sores and swelling), from Latin irritationem “incitement, provocation,” from irritare “to excite, provoke.” The sense “impatient or angry excitement” is recorded from 1703.
The emotional sense (by 1703) is younger than the physiological one, which persists alongside it. No reliable recent-generation shift is sourced.