Custom UD mugs
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1. You know it!
To totally disregard what someone is saying or said, and just agree with them completely whether or not they're right.
Example 1

Guy A : Sometimes I wonder if I should even be alive...
Guy B : You know it!

Example 2

Wife : Honey, I'm pregnant, and I don't think it's yours..
Husband : You know it!

Example 3

Guy A : Should I get a...
Guy B : You know it!
Guy A : But you didn't even let me finish...
Guy B : You know it!