HALFHEARTED
halfhearted, half-hearted, tepid, lukewarm
(adjective) feeling or showing little interest or enthusiasm; “a halfhearted effort”; “gave only lukewarm support to the candidate”
Source: WordNet® 3.1
Etymology
Adjective
halfhearted (comparative more halfhearted, superlative most halfhearted)
Lacking full energy, effort, commitment, or resolve.
Synonym: lukewarm
(obsolete) Lacking in heart or spirit; ungenerous; unkind.
Source: Wiktionary
Half"-heart`ed, a.
1. Wanting in heart or spirit; ungenerous; unkind. B. Jonson.
2. Lacking zeal or courage; lukewarm. H. James.
Source: Webster’s Unabridged Dictionary 1913 Edition