Definition
The direction toward the north magnetic pole of the Earth, which is the reference point that the needle of a magnetic compass points to. Magnetic north is offset from true north (the geographic North Pole) by an angle that varies with location, known as magnetic variation.
Plain English
The 'north' that your compass needle points to. It is not the same as the North Pole on a map -- it sits in a different spot, and the difference depends on where you are flying.
Context Anchor
You will see magnetic north when using a magnetic compass, setting or reading headings, and working with navigation systems such as a very high frequency omnidirectional range, or VOR.
Derivation
From the magnetic field of the Earth itself. The planet behaves like a giant magnet, and 'magnetic north' simply means the north end of that magnetic field -- the direction a freely turning magnet (a compass needle) naturally aligns with.
Why Pilots Care
All standard aviation charts, instruments, and VOR navigation reference magnetic north, so pilots must account for magnetic variation to avoid navigation errors.
Intuition Check
Do not assume there is only one kind of north. Magnetic north is compass north; true north is the geographic North Pole direction.
Example Sentence 1
VOR radials are oriented to magnetic north, so the 360 radial points magnetically north from the station.
Example Sentence 2
VOR radials are measured clockwise from magnetic north at the station.