1. (n.) The act of stimulating, or the state of being stimulated.

2. (n.) The irritating action of various agents (stimuli) on muscles, nerves, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity; irritation.

a high actuation aggravation agitation alpha decay animation arousal arousing atom-chipping atom-smashing atomic disintegration atomic reaction atomization bait beta decay bombardment bracer bracing breeding bribe bullet carrot chain reaction cleavage cordial direction disintegration series dissociation electrification emotion encouragement energizing enlivenment exacerbation exasperation exchange reaction excitation excitedness excitement exhilaration fillip firing fission fission reaction fomentation galvanization gamma decay incentive incitation incitement inducement inflammation influence infuriation inner-direction instigation interest invigoration invitation ionization irritation lathering up lure manic state motivation moving neutron reaction nonreversible reaction nuclear fission nucleization other-direction payment pep rally pep talk percentage persuasive perturbation photodisintegration pick-me-up profit prompting proton gun proton reaction provocation quickening rabble-rousing reanimation recreation refection refreshing refreshment regale regalement reinvigoration renewal reversible reaction revitalization revival revivescence revivescency revivification reward splitting the atom steaming up stimulative stimulus stirring stirring up stirring-up sweetener sweetening target thermonuclear reaction tonic vitalization vivification whet whipping up working up