half-hearted

(idiom) uninterested in something, unenthusiastic about something

Example Sentences:

Jeanette gave a half-hearted effort on her presentation. I’d like her to do it again.

My best friend made a half-hearted attempt to help me move into my new apartment.

Similar idioms:

1. half assed
2. heart is not in something
3. half-baked idea
4. cover one’s half