back door; rear door
Refers to a door at the back or rear of a building, often used for service or private access.
店の裏扉から荷物を運び入れた。
We carried the goods in through the shop's back door.
Compound of 裏 (ura, 'back') and 扉 (tobira, 'door'). The reading とびら becomes voiced to どびら due to rendaku.