Deceiving a person or people to somehow watch, or see the "Never Gonna Give You Up" video by Rick Astley.
Rick Rolling can also be a real life act of the music clip - normally by playing the song and having an impostor sing or dance to the video. Thus "Rick Rolling" the unsuspecting audience.
It is popular on video's that promise exclusive footage - such as a GTA4 gameplay, Or Halo3 exclusive.
Someone just came into the stadium dressed as Rick Astley and danced, while the music was playing. We all got Rick Rolled.
Clicking the link to a video of Rick Astley's "Never Gonna Give You Up", thus being Rick Rolled.