The Full Form of MPIN is Mobile banking Personal Identification number.

A personal identification number (PIN), or sometimes redundantly a PIN number, is a numeric or alpha-numeric password used in the process of authenticating a user accessing a system.

The personal identification number has been the key to flourishing the exchange of private data between different data-processing centers in computer networks for financial institutions, governments, and enterprises. PINs may be used to authenticate banking systems with cardholders, governments with citizens, enterprises with employees, and computers with users, among other uses.

In common usage, PINs are used in ATM or POS transactions, secure access control (e.g. computer access, door access, car access), internet transactions or to log into a restricted website.