back door

(noun) a secret or underhand means of access (to a place or a position). Synonyms: back door, backdoor. Example: "He got his job through the back door."

(noun) an undocumented way to get access to a computer system or the data it contains. Synonyms: back door, backdoor.

(noun) an entrance at the rear of a building. Synonyms: back door, backdoor, back entrance.