One who spoils; a plunderer; a pillager; a robber; a despoiler.

One who corrupts, mars, or renders useless.

A document, review or comment that discloses the ending or some key surprise or twist in a story, or the internal rules controlling the behaviour of a video game, etc.

(aeronautics) A device to reduce lift and increase drag.

(automotive) A device to reduce lift and increase downforce.

(US, chiefly politics, sports) An individual (or organisation etc.), unable to win themselves, who spoils the chances of another's victory.

(transitive, fandom slang) To mark (a document or message) with a spoiler warning, to prevent readers from accidentally learning details they would prefer not to know.

(transitive, fandom slang) To tell (a person) details of how a story ends etc.