Be halfhearted about something指某人完全不认真对待某事；做事心不在焉。

【例句】
I wish you weren't so halfhearted about this new project! Get serious!
我希望你不要对这个新项目这么不上心！认真点！

She was rather halfhearted in her attempts to find a job.
她在找工作时态度相当漫不经心。