runoff

noun

1. (countable, uncountable)That portion of precipitation or irrigation on an area which does not infiltrate or evaporate, but instead is discharged from the area.

   “The next series of high tides or large waves will tend to rebuild the berm and redam the stream. Ultimately, increased runoff due to fall or winter rains will raise the stream level to the point where it breaks through.”

2. (countable, uncountable)Dissolved chemicals, etc, included in such water.

   “The runoff of nitrates is poisoning the lake.”

   “Toxic runoff from rare earth mines in Myanmar is contaminating rivers that flow into Thailand, threatening the Mekong River and its basin's fisheries and farmland.”

3. (countable, uncountable)A second or further round of a competition, after other competitors (often all but the last two) have been eliminated.
4. (countable, uncountable)A second or further round of an indecisive election, after other candidates (often all but the last two) have been eliminated.

   “There will now be a runoff as neither front runner received more than 50% of the vote.”

   “It is one of the left's best ever results and will raise momentum for next month's final runoff where only the two candidates will compete against each other.”

   “Mr. Macron was unable to command more than a small plurality of support against several opponents in the first round of voting on April 10. Ms. Le Pen, who finished second, is his opponent in the runoff election on Sunday.”