single door; door that opens from one side
Refers to a door that has one leaf and opens in one direction, as opposed to a double door (両開き). Used in architectural and everyday contexts.
See also: 両開き
The door to this room is a single door.
I bought a refrigerator with a single door.
Compound of 片 (kata, 'one side') and 開き (hiraki, 'opening'), referring to a door that opens from one side only.