Definition - What does Spoiler mean?
A spoiler, in IT and elsewhere, is a message or image that reveals something significant about a piece of media or a piece of software. It is called a spoiler because it spoils the surprise for someone else who has not yet seen or used the thing that the message is about.
Techopedia explains Spoiler
People may use the term spoiler in software and gaming markets. For instance, advanced notices about features, operations or interfaces for new operating systems would be considered spoilers for people who have not yet used those operating systems. In other cases, a spoiler may come out for game, where somebody might review the game before its release and talk about its plot lines, play characteristics, characters or other aspects of the game that would normally be surprises to the person playing the game.
The term is also commonly used in reference to media, such as movies and TV programs, when significant plot points are revealed. The term "spoiler alert" is often used to warn people of an upcoming spoiler, so that they may stop reading in order to avoid any spoilers.