back door

Short definition from Wiktionary

Noun

1. 1
   A subsidiary entrance to a building or house at its rear, normally away from the street.
2. 2
   A means of access, often secret and unprotected, to something.
3. 3
   A secret means of access to a program or system.
4. 4
   A rear side door of a car, or at the back of a van.
5. 5
   The anus; (by extension) anal sex.
6. 6
   The rear side of the hole, furthest from the golfer.
7. 7
   Alternative form of back door.

Adjective

1. 1
   The path of a pitch which starts outside and then slides over the plate.
2. 2
   Achieved through indirect means.
3. 3
   Requiring consecutive cards on the turn and river to be achieved.

Verb

1. 1
   To attempt to accomplish by indirect means, especially when direct means are proscribed.
2. 2
   To enter a tube by accelerating from behind; to surf into an already formed hollow wave, in contrast to the normal method of slowing to allow a surfable wave to form.
3. 3
   To add a backdoor (a secret means of access) to a program or system.