If a person is chirpy, they are happy and active in a light, bright way. Think of a small bird singing — not sad, not slow, not heavy. A chirpy person greets you, talks a little fast, and seems ready for the day. We use it mostly about people and their mood, especially in the morning, or after small good news. You can also call a voice chirpy. It is friendly, everyday English, and you hear it a lot in Britain. You would not call a serious judge chirpy in court; it would sound wrong, almost teasing. Though actually, chirpy can sometimes mean "a bit too cheerful" if the room is sad and the person does not match it — but most of the time it is a kind word. The word you will meet is almost always this describing use, not a name for a thing.