1. (n.) The state or quality of being irritable; quick excitability; petulance; fretfulness; as, irritability of temper.

2. (n.) A natural susceptibility, characteristic of all living organisms, tissues, and cells, to the influence of certain stimuli, response being manifested in a variety of ways, -- as that quality in plants by which they exhibit motion under suitable stimulation; esp., the property which living muscle processes, of responding either to a direct stimulus of its substance, or to the stimulating influence of its nerve fibers, the response being indicated by a change of form, or contraction; contractility.

3. (n.) A condition of morbid excitability of an organ or part of the body; undue susceptibility to the influence of stimuli. See Irritation.

abhorrence abnormality abomination acute disease affection affliction ailment allergen allergic disease allergic disorder anaphylaxis antagonism antipathy asthma atrophy aversion bacterial disease birth defect blight cardiovascular disease chronic disease circulatory disease cold sweat complaint complication condition congenital defect conjunctivitis considerateness cosmetic dermatitis creeping flesh defect deficiency disease deformity degenerative disease delicacy disability disease disgust disorder distemper eczema empathy endemic endemic disease endocrine disease enmity epidemic disease exquisiteness fineness functional disease fungus disease gastrointestinal disease genetic disease handicap hate hatred hay fever hereditary disease hives horror hostility hyperesthesia hyperpathia hypersensitivity iatrogenic disease identification illness indisposition infectious disease infirmity irritability loathing malady malaise morbidity morbus mortal horror muscular disease nausea nervousness neurological disease nutritional disease occupational disease organic disease oversensibility oversensitiveness overtenderness pandemic disease passibility pathological condition pathology perceptiveness perceptivity photophobia plant disease pollinosis prickliness protozoan disease psychosomatic disease rejection repugnance repulsion respiratory disease responsiveness revulsion rockiness rose cold secondary disease seediness sensitiveness sensitivity sensitization shuddering sickishness sickness signs soreness supersensitivity sympathy symptomatology symptomology symptoms syndrome tact tactfulness tenderness tetchiness the pip thin skin ticklishness touchiness urogenital disease urticaria virus disease wasting disease worm disease