Flatline
The term flatline is usually used to describe an electrical measurement that shows no activity and therefore when represented, shows a flat line instead of a moving one. It almost always refers to either a flatlined EKG, or asystole, in which the heart shows no electrical activity, or to a flat EEG, in which the brain shows no electrical activity. (see also: Brain death.) Both of those specific cases are involved in various definitions of death.