The term bird has a very broad and general meaning. In its plainest sense, it refers to any feathered creature belonging to the class Aves, which includes all species of flying creatures such as eagles, sparrows, penguins, parrots, ostriches, etc. However, when used in a more colloquial manner, bird can also refer to anyone or anything that is small and seemingly insignificant, often used in phrases like "that's just peanuts" or "don't be such a chicken (little)".