This is a phrase used to alert someone on a message board that the following message contained plot 'spoilers', or details of a show which if known about beforehand, spoils the viewing of the show.
The SPOILER ALERT phrase would appear in a message's title (such as usenet headers), or on messageboards where the message is expanded.
Lately, people seem to put the spoiler immediately after the 'spoiler alert' which ruins the idea of a spoiler alert in the first place, so they're letting you know they're spoiling it on purpose.
Dec 31, 2012
Looking for tweets for SPOILER ALERT.
‘SPOILER ALERT’ has been looked up 128 times, added to 1 list, commented on 1 time, and is not a valid Scrabble word.