magnetic needle

American  

noun

1. a slender magnetized steel rod that, when adjusted to swing in a horizontal plane, as in a compass, indicates the direction of the earth's magnetic fields or the approximate position of north and south.

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magnetic needle British  

noun

1. a slender magnetized rod used in certain instruments, such as the magnetic compass, for indicating the direction of a magnetic field

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Etymology

Origin of magnetic needle

First recorded in 1840–50

Example Sentences

Finding the magnetoreceptors responsible for triggering these neurons has been like looking for a magnetic needle in a haystack.

From Science Magazine • Jun. 23, 2016

Last week Bendix Aviation Corp. announced a new automatic compass that makes the old magnetic needle* look as obsolete as a warrior's spear.

From Time Magazine Archive

He said: "Nothing must deflect the magnetic needle."

From Time Magazine Archive

Astatic, a-stat′ik, adj. having a tendency not to stand still: losing polarity, as a magnetic needle.

From Chambers's Twentieth Century Dictionary (part 1 of 4: A-D) by Various

On this as on the previous voyage, Hudson made some observations on the inclination or “dip” of the magnetic needle, and he is probably the first Englishman who had done so.

From The Sea: Its Stirring Story of Adventure, Peril, & Heroism. Volume 3 by Whymper, Frederick