If you say that someone is a natural, you mean that they do something very well and very easily. He's a natural with any kind of engine.

What does it mean if something is natural?

: existing in nature and not made or caused by people : coming from nature. : not having any extra substances or chemicals added : not containing anything artificial.

Which are natural things?

Natural things : plants,animals,birds,fish and citizenry are the natural things. This stuff is the gift of nature.