Miniboss

A miniboss is a minor boss. Minibosses only appear in Super Metroid, and since of their lack in the other Metroid games, they are nowadays considered to be bosses. For example, Crocomire is the miniboss of Norfair, but there is no boss, therefore he should be considered a boss, even if defeating him does not unlock one of the statues guarding the entrance to Tourian.