1For something hot to lose heat and become cold, especially food or drinks.
冷めないうちに召し上がってください。
Please eat it before it gets cold.
お風呂が冷めてしまったので、もう一度沸かした。
The bath water had gone cold, so I reheated it.
熱いお茶もすぐに冷めてしまう季節になった。
It's become the season when even hot tea quickly cools down.
電話が長引いて、夕食が冷めてしまった。
The phone call went on too long, and dinner got cold.
2For emotions, enthusiasm, or interest to fade and lose intensity - also used for romantic feelings cooling off.
最初は夢中だったが、半年もすると熱が冷めてきた。
I was obsessed at first, but after about six months my enthusiasm cooled off.
二人の関係はいつの間にか冷めてしまったようだ。
It seems their relationship has cooled without anyone noticing.
あの騒動も、数日たてば人々の関心は冷めるだろう。
Once a few days pass, people's interest in that uproar will probably die down.
3To have a cold, detached look or attitude, showing little emotion.
彼はいつも冷めた目でこちらを見る。
He always looks at me with a cold, detached gaze.
冷めた態度を取られると、こちらも話しづらくなる。
When someone acts so detached, it makes it hard to talk to them.