[count] a person or thing that spoils something: such as

a political candidate who cannot win but who prevents another candidate from winning by taking away votes

b chiefly US :a person or team that surprisingly defeats a competitor that is expected to win

information about the things that happen in a movie, book, etc., that spoils the surprise or suspense for someone who has not seen it or read it yet

a long narrow part on the back of an automobile that prevents it from lifting off the road at high speeds

a part of an airplane's wing that may be raised to control the amount of lift produced by the wing