Betaille is a pretty broad assortment of meanings, in any area, but probably has some meanings that differ from area to area. My understanding of it is it usually means animal, generally, but it can also carries a "beastly" meaning, just as it can in English.
Another word close to it that is used in my area of Acadiana (Mamou) is tataille, now that word to me means a type of monster, but is apparently not commonly used other places.