Term used for video
game sequels that are completely unrelated to the first one. Some infamous examples include Super Mario Bros
2,
Zelda 2: The Adventure of
Link, and Castlevania 2: Dracula's Curse. Games like these have different gameplay mechanics and sometimes completely different enemies and final bosses (Except for Castlevania 2 in this case).
For all 3 games mentioned, they have elements that are carried on to later games of their series.