grayout

The perception of a transient loss or dimming of light, color, or clarity in one's vision due to a lack of oxygen reaching the brain. The intense g-forces can cause grayouts in fighter pilots, but they are usually still able to maintain control of the vehicle. People tend to experience grayouts pretty quickly when they're exposed to high levels of carbon monoxide—that's why it's so dangerous. I can feel myself verging on a grayout—can we please sit down?