(Blackout; Swoon) To blackout or to faint in a dream means suffering from great sorrow.
It is always a bad omen if you see signs of collapse or illness in your dream, whether you are the sufferer yourself, or whether you tend someone who is ill.
If you dream that you are fainting, then you are probably having a blood sugar drop. This can also represent that you are feeling overwhelmed and your dream is telling you to take a break and/or a vacation. See Breakdown.