Gaining access to a restricted communications channel by using the session another user already established. Piggybacking can be defeated by logging out before walking away from a workstation or terminal or by initiating a screensaver that requires re-authentication when resuming.
Piggybacking also refers to someone allowing another person to follow right after them into a restricted area. Also known as "tailgating," this may be done on purpose by a disgruntled employee or just out of carelessness. See replay attack
Using a Wi-Fi hotspot of neighbors who have not secured their network. See Wi-Fi piggybacking
and Wi-Fi hotspot
Embedding the names of popular brands or companies into the hidden meta-data of a Web page in order to rank high up on a search engine's results page. See meta tag