生ぬるい (namanurui) means “lukewarm”

More examples

冷蔵庫に入れ忘れて、牛乳が生ぬるくなってしまいました。rei zō ko ni i re wasu re te gyū nyū ga nama nu ru ku na tte shi ma i ma shi ta

I forgot to put the milk in the refrigerator, and it became lukewarm.

Marks a middle temperature that feels insufficiently heated rather than distinctly hot or cold.

ぬるいnurui: Describing something with less heat than expected, without being distinctly cold.

十分に温まっておらず、熱くも冷たくもない状態である。jū bun ni atata ma tte o ra zu atsu ku mo tsume ta ku mo na i jō tai de a ru

生ぬるい (namanurui) combines 生 (nama, "raw or incomplete") with ぬるい (nurui, "lukewarm"), describing something that has not become properly hot.

The adjective 生ぬるい (namanurui) can describe both a drink and an attitude, with the latter meaning lacking energy or firmness.