Definitions
1.nounOne who spoils; a plunderer; a pillager; a robber; a despoiler.
2.nounOne who corrupts, mars, or renders useless.
3.nounA 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.
4.nounA device to reduce lift.
5.nounA device to reduce lift and increase downforce
6.nounAn individual (or organisation etc.), unable to win themselves, who spoils the chances of another's victory.
7.verbTo mark (a document or message) with a spoiler warning, to prevent readers from accidentally learning details they would prefer not to know.
8.verbTo tell (a person) details of how a story ends etc."I've been spoilered, so I doubt I'll be able to enjoy the final episode."