A code that prevents a wireless phone from unauthorized use. When explicitly locked, and each time the phone is turned on, it will prompt the user to enter the code before it will allow a call to be placed. Calls, such as emergency or other specially-programmed numbers, may be placed without entering a lock code.
Typical default codes include the last four digits of your phone number, the last four digits of your social security number, "1234", or "0000".