Pacu (Portuguese pronunciation: [paˈku]) is a common name used to refer to several common species of omnivorous South American freshwater fish that are related to the piranha. Pacu and piranha don't have similar teeth, although the main difference is jaw alignment; piranha have pointed, razor-sharp teeth in a pronounced underbite, whereas pacu have squarer, straighter teeth like a human in a less severe underbite, or a slight overbite.
Courtesy of Wikipedia.