What are bodies?

Question

By bodies I mean the bodies of organisms, not inanimate objects with mass.

Answer 1

Strictly speaking, we can think of bodies as referring to substances (matter-form composites) which are possessed of at least some of the animating capacities. Hence, animals are bodies even though they lack a rational soul. It is a material substance.

However, a much more helpful definition would be to define body as that which is quantitatively contained in space. If we are using the term "body" strictly to include organisms, as you noted in the terminology of your question, it must be only with respect to things possessing length, width, and height.