Keyboard ghosting is when certain key combinations fail to register because the keyboard's matrix can't handle simultaneous presses. To test: open an online keyboard test and press 3-4 keys simultaneously in combinations you use often (e.g., W+A+Shift for gaming, or Ctrl+Shift+S for shortcuts). If one key doesn't light up while the others are held, that combination ghosts. Most budget membrane keyboards ghost on 3+ simultaneous keys. Mechanical keyboards with proper anti-ghosting handle 6+ keys (6-key rollover or 6KRO). Full N-key rollover (NKRO) keyboards register every key simultaneously regardless of combinations. Ghosting is a hardware limitation — no software fix exists. If ghosting impacts your work or gaming, upgrade to a keyboard that advertises NKRO or anti-ghosting.