light as a feather

When you speak of someone or something as being light as a feather, it means that they are so light it seems like they are light as a feather. This is true in many different situations such as a cake or pastry which is very delicate and airy, and therefore seems light as a feather. A person who is told they are light as a feather, are typically very light in weight and a thin person, therefore they seem lighter than most other people.