a further competition/contest, race, or election that takes place after an inconclusive result (such as a tie) in order to determine the outcome;
e.g. They held a runoff tennis match because the original match had been interrupted by rain when the scores were equal.
(noun)
the process of precipitation (rain, snow, etc.) draining away from an area of land and eventually reaching streams or other water bodies, often carrying material such as sediments with it, or the water and dissolved material that drains off in this way;
e.g. The runoff from the farmlands eventually reaches the river.