Douglas Harper's Etymology Dictionary
1805, from un- (1) "not" + enthusiastic (adj.). Related: Unenthusiastically.
Wiktionary
a. Without enthusiasm; unexcited.
WordNet
adj. not enthusiastic; lacking excitement or ardor; "an unenthusiastic performance by the orchestra"; "unenthusiastic applause" [ant: enthusiastic]
Usage examples of "unenthusiastic".
A boy then presented the Mayoress with a bouquet of chrysanthemums, there was unenthusiastic applause, and young Mr Perse returned to his place behind the scenes by way of a swing door which led to a passage which, in its turn, led to the dressing-rooms.
But he'd been a loving man in his lustless way, and his wife Bernadette had shared his indifference to sex, so his unenthusiastic member had never been a bone of contention between them.
It was a tiny shop, boasting an unenthusiastic window display of old hardbacks, mostly with a Scottish theme.
The sounds are of a tiny, unenthusiastic audience applauding the death scene in some tragedy: it is the two masseurs walloping and potching at the flesh of their victims, men half-clad in sheets and stretched out across marble slabs.