Did someone leave a window open? It's chilly in here! That word means "cold," and it can also mean that someone's acting in a frosty way.
The main meaning of chilly is cold, but this word is often used for emotions too, just like "warm." A warm person is loving and kind, but a chilly person is unemotional, distant, and quiet. Chilly people are often called "aloof" — another word for someone who's not acting like a people person. "After you turned them in for cheating on their homework, they gave you a chilly reception."