What does anal bonus mean?

anal bonus meaning in Urban Dictionary

full-page pictures in "Prude" Magazine featuring somebody (male, feminine, or somewhere in between) becoming anally penetrated in an atypical fashion. The definition of became an interjection used frequently by intoxicated party-goers in rural places in Western nyc during the late 80's to express their substance caused euphoria. The phrase's usage faded using demise of this magazine.