The state of being completely shocked or amazed; extreme astonishment.
From flabbergast (origin uncertain, possibly from Dutch 'flabber' meaning to stammer, or onomatopoetic), combined with the suffix -ation to create a noun form. The root word flabbergast emerged in English in the late 1700s.
Flabbergastation is so rare that most dictionaries don't even list it—it's basically a made-up word that *sounds* real because English lets us add -ation to almost any verb, like how we can say 'the flabbergastation of the audience' instead of just 'their astonishment.'
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