When you are impressed by something someone says or does and you try and be cool but fail.
Example:

Girl: *does a backflip*
Boy: Dayuuum!!!
Girl: *looks at boy in a strange way as if they are a disease*
by WeirdInAWeirdWay February 10, 2021
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Da•yuuhm
(Slang)
Definition: Any particular happening that comes as a surprise to one.
"I got a 100% on my math test: DAYUUUM!"
by Canned bread November 23, 2013
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