Is there ways to define ?

Question

the north direction

Answer 1

The earth spins around an axis. When the sun rises, have the sun to your right. The way you are facing is north.

Answer 2

The most direct route to the north pole along the Earth's crust.

That's off the top of my head but I think it's appropriate.

Answer 3

The most direct route to the north pole along the Earth's geoid (not crust -- that includes mountains and valleys).

Answer 4

There is a definition here.