A terror bird is a Phorusrhacidae, a meat eating, flightless bird that was a large predator during the Cenozoic Period. More information can be found on the UK site BBC, Science Daily and several other websites.

Yes because Kelenken is a genus of giant flightless predatory birds of the extinct family Phorusrhacidae, or "terror birds". The type and only species is K. guillermoi, first formally described in 2007 after the find in 1999. It is the largest known member of the family.

The "terror birds" (Phorusrhacidae) were large carnivorous Flightless Birds that lived in South America during the Cenozoic era (from about 2 to 60 million years ago).

Standing 1 to 3 meters (3-10 feet) in height, they were one of the dominant predators of their time. Their closest modern relatives may be the seriema birds of Brazil, Argentina, and Paraguay.

Titanis Walleri. This bird is known from the early Pleistocene (Ice Age) of Florida. It is the last known member of the family Phorusrhacidae, a group of large, flightless birds which evolved in South America. This creature had an estimated body height of 3 meters (if it stood fully erect, and 2.5 meters in more normal situations). Titanis really had arms instead of wings.