Beasthuman is a creature that has a number of bestial features, but is a human in their nature.

This definition follows the Modifier-Nature structure, and in its unabridged form sounds as "Beastmorphic human". The adjective "beastmorphic" is a modifier that denotes the family or species of a creature from which additional features were taken. The noun "human" denotes the nature and base species of a creature.

A typical beasthuman has the following features:
- The torso, pelvis, arms and genitals are structurally identical to those of a human.
- The head, tail and lower limbs are structurally identical to those of a beast.
- If a beast has no legs (such as fish, marine mammals, snakes or slugs), then a beasthuman will have a corresponding tail instead of legs, and structurally resemble a mermaid.
- The appropriate body covering such as fur, feathers, scales, skin, carapace, etc.
- The structure and proportions of the body are balanced enough to allow a beasthuman to remain bipedal, and the bestial parts of their body to function normally with human ones.
- The intelligence and behavior are identical to those of a human.
- By default, all unmentioned features are identical to those of a human.

The structure of this definition allows to change the modifier or nature in order to specify the source of additional features, the main species, gender and age of a creature. Therefore, the same beasthuman can be named with such words as: beastman, bovinehuman, bullhuman, bovineman, bullman.