Third person singular or plural form: makes someone feel very happy, excited, and full of energy.
From exhilara(te) + -s. Exhilara(te) comes from Latin exhilarare, 'to make cheerful.' The verb form appeared in English by the 16th century.
Interestingly, 'exhilerate' (with an 'e') is an older spelling, but 'exhilarate' (without the 'e' in that position) became standard—a small spelling shift that happened during standardization of English.
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