a large flat object that you open when you want to enter or leave a building, room, or vehiclea little cottage with a red door
The door creaked slowly open.
There was a draught coming from under the door.
open/close/shut the door: The police officer told him to open the car door.
 Shut the door – it’s cold in here!
knock on the door  (=so that someone knows you are there): I knocked on the door and a voice answered ‘Come in’.
 be at the door  (=be outside the door to someone’s house): There’s someone at the door.
 answer/get the door  (=go to your door to see who is there): Go and answer the door, will you?
 bang/slam the door  (=close it noisily): He ran out, slamming the door behind him.
 door to/into: The door to the kitchen was open.
 back/front/side etc door: Be sure to lock the back door when you leave.
 bedroom/shed/car etc door: The bathroom door was shut.