The most common definition that you will most likely hear is the species level, but I don't think you will get much mileage out of this one as the kind as described in xian mythology appears to have categories that include obviously different species as the same kind.
Creationists would like to define “kind” in terms of interbreeding, since the Bible describes different living things as “multiplying after kind,”
Creation biologists have proposed a number of possibilities for the created "kinds": Humanity — Creationist Sigrid Hartwig-Scherer concluded that H. erectus/ergaster, Neandertals and H. sapiens were members of the same basic type (which corresponds to a monobaramin) Homininae with the fossils called Australopithecus afarensis, A. anamensis, A. africanus, A. robustus, A. aethiopithecus, A. boisei and possibly Ardipithecus ramidus assigned to another basic type, Australopithecinae. Felidae — Creationists from Creation Ministries International and the Institute for Creation Research have proposed that the original kinds were comparable to the Liger and the Tigon. Canidae — Similar to the kind associated with cats, it is proposed that all canines had a common ancestor. Camelidae — Including both the camel and the llama, which are reproductively compatible, their hybrid offspring being known as "Camas." Bovidae — Including Cattle, Buffalo, Bison, and Yaks. Equidae — Including Horses, Zebras, and Asses. Caprinae — Including Sheep, Goats, and ibex. Crocodilia — Including all the varieties of alligator, crocodile, and gharial. Elephants — African and Indian elephants can hybridize yet they are not even classified in the same genus. Thus the created kind corresponds roughly to the family level of taxonomic classification, and possibly even the order with the notable exception of humanity.