One-Time Password definition in Computer Security terms:
Definition(s): Involves the use of an identical OTP generator on the peer and authenticator. The generator iterates a secure hash function a specified number of times using a passphrase and random seed as the initial input. After each successful authentication transaction, the number of iterations is reduced by one, resulting in a unique series of passwords.
Source(s): NIST SP 800-97
reference: CSRC Glossary