Coil Whine
A high-pitched electrical noise from a laptop's power components, most noticeable at very high frame rates.
Coil whine is a faint, high-pitched buzzing or squealing caused by electrical components (inductors or coils) vibrating as current passes through them. It is most common when the GPU is pushing very high, uncapped frame rates, such as in menus or simple games.
It is an electrical phenomenon, not a fan or mechanical fault, and is usually harmless. Its severity varies from unit to unit even within the same model, and capping frame rates or enabling V-Sync often reduces or eliminates it.
Why it matters when buying
Coil whine is hard to predict before buying, but you can minimize it: cap frame rates with G-SYNC plus a frame limiter rather than running thousands of FPS uncapped. If a review unit whines badly, it is worth checking the return policy.