Things that are dreamy seem slightly strange and unreal, but in a lovely way. A dreamy tune on the radio might make you close your eyes and smile.
Your favorite tea shop might have a dreamy atmosphere, and your favorite movie might be slow and dreamy, with dreamlike images and meditative music. If a person is dreamy, she tends to live in her head, thinking or daydreaming. Informally, you can also describe something or someone that's wonderful or nice to look at as dreamy: "He's my favorite singer, and he's so dreamy." This casual meaning began as US teen slang in the 1940s.