Wastebasket taxon
Regular taxa are supposed to be monophyletic. By definition, wastebasket taxa are either paraphyletic or polyphyletic. Their name may still be very useful to biologists, because its members may be an important evolutionary grade. Antelopes are a group which is ecologically very important, and have many similar features. However, they are not monophyletic. Species are called 'antelopes' if they look like one.