It just is short form for Boa Constrictor Imperator which is Rauri's "proper" name for what he is I guess you'd say. He's also referred to as a Columbian Red-Tailed Boa and a Common Columbian Boa as well as far as I've been told.
Thanks for all the compliments folks. Rauri just gets better looking each shed and he truly is a lovely big snake with a perfect temperment and a lovely feeding response.
~~Jo~~