- noun a security system designed to reduce the risk of an unauthorised user connecting to a computer installed with dial-in networking
- noun a security system that is used to reduce the risk of any unauthorised user connecting to your computer if you have installed dial-in networking. With callback, you use your communications software and modem to dial the remote computer and enter your name and password. The remote computer then hangs up the telephone line and calls you back on a preset telephone number.
- A security measure in which a network verifying the user name and password of a caller terminates a received call, then places a new call to the terminal associated with that user name and password. This procedure serves as an additional safeguard in case a user name and password are stolen.
- noun the practice of making a second or further attempt to contact a person for interview, random sampling etc., after the first attempt has failed