Plain English Meaning

Tiny adjustable magnets inside the compass that can be turned to cancel out the magnetic interference caused by the aircraft itself, so the compass reads more accurately.

Full Definition

Small adjustable magnets built into the magnetic compass housing that produce their own magnetic fields to cancel out unwanted magnetic influences from the aircraft's own electrical systems and ferrous metal components. They are adjusted during a procedure called 'swinging the compass' to reduce deviation errors on the cardinal headings.

Context Anchor

Seen in magnetic compass theory, compass inspection, and compass checks, especially when discussing why a compass may not exactly where the aircraft is .