Definition of "enthusiast"

But Charles Aubyn (for it was he) had, like most enthusiasts, overcalculated the influence of his eloquence; surprise had alone procured him a hearing, and the bold cavaliers around were little in the mood for a homily.

1834, L[etitia] E[lizabeth] L[andon], chapter IV, in Francesca Carrara. […], volume III, London: Richard Bentley, […], (successor to Henry Colburn), page 28

I would challenge any rock enthusiast to refrain from tapping his/her foot when listening to such music.

2010, Niamh Nic Daeid, Fifty Years of Forensic Science: A Commentary