A poli (pl. polis) is a sapient being. Polis are much like humans except that polis have no external hind legs. Their leg and foot bones are contained entirely inside the butt area. They walk on their hands and bottom, and they have a large fat pad on the bottom for cushioning.
Soldiers who lose legs in combat may choose to go live with the polis.
|Out-of-universe information (spoiler)|
"Poli" comes from "roly-poly". A name for this race prior to the fourth quarter of 2008 was "weebles", after Playskool's toy.