(idiomatic) To do something pointless or unnecessary; to try doing something already done.

(simile) irrefutably or unquestionably dumb

(simile, slang) Very stupid.

plural of stage door

A miniature door, usually set into the base of a tree, behind which may be a small space where people can leave notes and gifts.

plural of fairy door

A type of door having the central panels filled with horizontal louvres.

plural of plantation door

One of 72 counties in Wisconsin, United States. County seat: Sturgeon Bay. It is situated on the Door Peninsula.

(informal) The extinct flightless bird Bullockornis.