The act of speaking about something in advance; prediction or advance announcement.
From 'forespeak' + '-ing' (gerund/present participle suffix). The '-ing' suffix converts the verb into a noun form representing the action itself.
Forespeaking is essentially what spoilers do—they're technically just forespeaking about the plot. The word shows how language marked 'ruining the surprise' as a legitimate category of speech.
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