Synonyms for Half-hearted:

adj.

half-hearted (adjective)
unenthusiastic, indifferent, apathetic, lukewarm, cool, perfunctory, uninterested, listless, passive, neutral.
hesitant (adjective)
unwilling.
indifferent (adjective)
neutral, uninterested, dispassionate, cool, perfunctory, easygoing, lukewarm, disinterested, indifferent, impartial, cold, uncaring, insouciant, apathetic, passive, unconcerned, nonchalant, unwilling, detached.
lackadaisical (adjective)
disinterested, unconcerned.
lukewarm (adjective)
cold.
unenthusiastic (adjective)
unenthusiastic.

n.

listless, restless, fed up, blase, bored, unenthusiastic, uninspired, world-weary.

Other synonyms:

Other relevant words:
uninspired, listless, unenthusiastic.