IPA: /ˌhæfˈhɑːrtɪdli/
KK: /hæfˈhɑrtɪdli/
In a way that shows little enthusiasm or interest.
She halfheartedly agreed to help with the project, but it was clear she didn't really want to.
Halfheartedly → It is formed from "half" (from Old English "healf", meaning part of something) and "heartedly" (from "heart" (meaning the center of emotion) and the suffix "-ly" (meaning in a manner of)). The word describes doing something in a manner that is only partially committed or enthusiastic, as if only half of one's heart is involved.
Think of doing something with only 'part of yourself' ('half') and not fully engaging your 'heart' — that's why halfheartedly means to do something without full commitment.