Spoilers was the term used to refer to any piece of future information, a thing or event that hadn't yet happened but that someone knew about due to time travel. River Song and the Eleventh Doctor frequently used the term "spoilers" when they could not tell the other something because it involved details about the other's future life. Because the Doctor and River were both time travellers and because they met in the wrong order, anytime they were together at least one of them had information about the other's future. Using the term "spoilers" to answer a question let the other person know that the answer was something that they could not tell the other without risking damaging time.

Neither River nor the Doctor was the originator of the term; the term itself functioned as an information loop. The Tenth Doctor first heard the term from River, when they met in The Library, but River first heard the term from the Eleventh Doctor in Hitler's Germany. (TV: Silence in the Library, Let's Kill Hitler)

Behind the Scenes

• The reference was an intentional jibe by writer Steven Moffat at fans who want to know details of forthcoming episodes of Doctor Who before they air.
• The first time the phrase "Spoiler" was said, was by River Song, in the first meeting with her, in TV: Silence in the Library.

For information on how spoilers are treated on the Doctor Who Wiki, see Tardis:Spoiler policy.