Th old argument. What is a big bore?

Many say the .375 is actually a medium bore. The only reason it is called a "big bore" is that it is the minimum that can be used to hunt DG in some African countries. Minimum being a key word.

Is it just adequate to do the job or more than adequate?

Compared to a .30-06 it is a big bore but is it if stood beside a .450 or a .500?

Comments please.