Plain English Meaning
A small metal disk inside an instrument that quietly slows down jittery movements so the needle reads smoothly instead of bouncing around.
Full Definition
A non-magnetic metal disk, typically aluminum, mounted on a rotating shaft inside certain flight instruments and positioned within the field of a permanent magnet. As the disk rotates, the magnet induces eddy currents in it, and those currents create a drag force that opposes the motion. This drag smooths out rapid fluctuations in the instrument's reading without affecting its steady-state response.