Refers to modest outbuildings used for shelter or storage. A shed is usually one story, typically has one or more open sides, and may be covered by a lean-to roof with one high pitched plane covering the entire structure. It may be leaning against a permanent structure or standing alone. The special purpose of the shed is typically indicated by a defining word prefixing (e.g., "cowshed," "woodshed," "train shed").

Source: AAT

http://vocab.getty.edu/page/aat/300006411