1. (n.) 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.

2. (n.) 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. (n.) 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.

adverse circumstances adversity affliction aggravation agitation algesia amplification animation annoyance arousal arousing augmentation blight bummer care chafe contentiousness cross curse deepening deliberate aggravation deterioration difficulties difficulty disapprobation disapproval discontent displeasure dissatisfaction downer electrification embittering embitterment enhancement enlargement exacerbation exasperation excitation excitement exhilaration festering firing fomentation fret gall galvanization hard knocks hard life hard lot hardcase hardship heightening incitation incitement increase inflammation infuriation instigation intensification irritant lathering up magnification pep rally pep talk perturbation plight predicament pressure provocation rabble-rousing rankling resentfulness resentment rigor sea of troubles sensitiveness sharpening sore sore spot soreness souring steaming up stimulation stimulus stirring stirring up stirring-up stress stress of life tenderness trial tribulation trouble troubles vale of tears vexation vicissitude whipping up working up worsening