Wiktionary
n. A magnetized pointer (usually marked on the North end) within a compass, free to align itself with the Earth's magnetic field.
Usage examples of "compass needle".
Make the atoms of blood and iron line up the way a compass needle lines up to face north.
Dumont d'Urville (1790-1842), was sailing along the Antarctic shore and found a section where the compass needle pointed nearly straight upward.
The compass needle slowly aligned to point hard to the east as I traveled south, and I wound up turning east on Fifty-fifth, toward the University of Chicago and Lake Michigan.
A faint cry drifted up from the sea of tossing yellow below, it might have been a baby's cry, or perhaps only a distant crow, but her head swiveled toward it, like a compass needle pointing to true north.
A safe distance away, she paused to check the air left in her tanks on the pressure gauge, mark her position on a Global Positioning System satellite minicomputer, eye the compass needle in relationship to the underwater habitat where she and her brother were living while studying the reef and note the reading on her bottom timer.
In its withdrawal, however, it pulls us along behind, and, like a compass needle in a magnetic field, we become a sign that points to it even in the midst of its concealedness.