When nothing's moving, that's stasis. If your negotiations about who does the dishes have reached a standstill, you know what stasis is. Yet the kitchen sink looks worse every day.
Sometimes opposing forces are equal in power, and since neither is stronger than the other, the result is a state where neither can gain any headway. This state is called stasis, and it is basically a stoppage of movement. In medicine, stasis describes the stopping of any bodily fluids from flowing, usually by an obstruction. The same idea is seen in literary stasis, where there is no forward movement in a story.