a large North American bird that eats fish and makes a noise like a laugh 潜鸟（北美食鱼大鸟，叫声似笑声） - (also loony)(informal, offensive)
a person who has strange ideas or who behaves in a strange way 狂人；疯子；怪人 That guy’s a real loon. 那家伙真是傻子。
Word Originsense 2 late 19th cent.: from loon (referring to the bird's actions when escaping from danger), perhaps influenced by loony.sense 1 mid 17th cent.: probably by alteration of Shetland dialect loom, denoting especially a guillemot or a diver, from Old Norse.