WordWeb Online

1. An undocumented way to get access to a computer system or the data it contains
   - back door
    
2. An entrance at the rear of a building
   - back door, back entrance
    
3. A secret or underhand means of access (to a place or a position)
   - back door

Derived forms: back doors

Type of: access, access code, exterior door, outside door

Encyclopedia: Backdoor