means A person competing with another for the same goal, prize, or position — your direct competitor.

from From Latin 'rivalis,' which literally meant someone who shares the same 'rivus,' or stream. Picture two neighbors drawing water from one river — useful when it flows, but a flashpoint when it runs low. From that shared-water squabble the word came to mean any two people contending over the same thing, and English borrowed it in that sense in the late 1500s.