I was going to joke it's about medium sized things but size is not a reasonable distinction (neither absolute size nor number of "parts") and you quickly run into the problem how organisations (i.e. groups of humans acting together) or machines (e.g. a car) are fundamentally different.
I guess the definition really is pretty fuzzy and arbitrary. It's "obvious" why a bunny is biology and a car or company is not, but it's not quite so obvious why a virus or an android isn't.
Heck, xenobiology seems to be inherently problematic because alien life would defy all classification. Imagine the "xenomorph" from the Alien universe. Would that be considered a reptile? Is it even a vertebrate? What animal rights legislation would apply to it if any? Would a "grey" count as a person? We like to justify these laws with biological categories but what do we do when faced with situations where the categories break down?
EDIT: Is an artificial, viable sheep-human hybrid an animal or a human?
> We like to justify these laws with biological categories but what do we do when faced with situations where the categories break down?
Change them to suit the world as we understand it.
The reality is that classifications as strict rules are a fantasy we choose to believe in, but at the end of the day, classifications are descriptions, and so we have to mutate them to help us describe things as best we can.
The reality is we work to the level of detail and accuracy we need. Rigidity in labels and classification is probably a sign of a lack of understanding, because almost everything ends up being broken down more at some point, and exceptions are found that break the rules.
