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2.
showing the approval of something said by a group member
Tyler:aye i just got that shit mw2

Justin:saydat!

Tyler:DAT!!
by justin barnes January 02, 2010
 
1.
A phrase started by the 11th notationally ranked boys soccer team at Stadium High School meaning to approve of something. Also used in response to a question or phrase of comedic nature. Also used in pairing with "Whats Good Though".
"Yo man, we just won 5-0"
"Oh yup, Say Dat"

Or

"Did you see the ass on that chick"
"Haha Say Dat"
by Say Dat April 14, 2010