The expression, “half-hearted,” is typically used to describe an unenthusiastic effort or disinterest in performing a particular action. This expression invokes the image of a “half-heart” to show a lack of enthusiasm about a certain activity.
“It was obvious from his half-hearted kicks that the boy did not share the others’ enthusiasm at playing soccer.”
“After having lost their chance at winning the championship, the disappointed basketball players half-heartedly gave their opponents congratulations.”
*Note that in situation 2, half-hearted is used as an adverb to describe the degree in which the players gave their congratulations to their opponents.