absorbing or controlling possession of the mind by any interest or pursuit; lively interest: He shows marked enthusiasm for his studies.
2.
an occupation, activity, or pursuit in which such interest is shown: Hunting is his latest enthusiasm.
3.
any of various forms of extreme religious devotion, usually associated with intense emotionalism and a break with orthodoxy.
Origin: 1570–80; < Late Latinenthūsiasmus < Greekenthousiasmós, equivalent to enthousí(a) possession by a god (énthous, variant of éntheos having a god within, equivalent to en-en-2 + -thous, -theos god-possessing + -iay3) + -asmos, variant, after vowel stems, of -ismos-ism
archaic extravagant or unbalanced religious fervour
4.
obsolete possession or inspiration by a god
[C17: from Late Latin enthūsiasmus, from Greek enthousiasmos, from enthousiazein to be possessed by a god, from entheos inspired, from en-² + theos god]
c.1600, from M.Fr. enthousiasme, from Gk. enthousiasmos, from enthousiazein "be inspired," from entheos "inspired, possessed by a god," from en- "in" + theos "god" (see Thea). Acquired a derogatory sense of "excessive religious emotion" (1650s) under the Puritans; generalized
sense of "fervor, zeal" (the main modern sense) is first recorded 1716.