Lukewarm means barely warm, neither hot nor cold. When your hot chocolate sits too long and cools down to just slightly warm, it's become lukewarm. When you test bathwater with your hand and it feels tepid instead of pleasantly hot, that's lukewarm too.

The word also describes an unenthusiastic response. When your friend reacts to your exciting news with just “oh, that's nice” instead of genuine excitement, their reaction is lukewarm. A lukewarm review of a movie suggests the critic thought it was just okay, nothing special. A lukewarm welcome means people greeted you politely but without much warmth or enthusiasm.

Think of lukewarm as the temperature equivalent of a shrug: not cold enough to reject, but not hot enough to embrace. When you're passionate about something, like a favorite book or hobby, you don't want others responding with lukewarm interest. You want them to share your enthusiasm, not just acknowledge it halfheartedly.