Furrin_Gok said:
Okay, in that case: Any specific body part getting larger is likely unnatural. The entire body would be natural, but not the specific limbs or portions.

My use of the word 'natural' was used to distinguish between the two terms. Growth sounds natural as it is generally used to describe an organism getting larger over time due to aging (usually), with body parts maintaining similar size proportional to the rest of the body. Expansion sounds as though it is specific to a single region of the body over a short period, which is generally unnatural. Though not everything natural grows at the exact same rate. Human heads grow slower than the rest of the body, and there are of course example of dynamic 'growth' such as puffer fish and erections.