The term "beastman" appears to be a broad classification for any non-human person in Allraan that may share characteristics of an animal. Specific sub-types of beastman exist. For example, Yuferius VII is both a shi'arc, specifically, and a beastman, broadly.
Beastmen are known as making for the most ferocious troops in battle, so during wars beastmen mercenaries are especially sought after. However, as beastmen are usually contracted as individuals, they often ending up fighting their kinsmen on the battlefield.