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1.
To Use "The Dude" on some one - to invoke the word "dude" when
referring to someone directly in an (often last-ditch) effort to relate
to that person on a less formal or "guy to guy" level.
Ex. 1.: "Then, I used the dude on him, but he still didn't get it?"
Ex. 2.: "I used the dude on him. I said, "hey, dude; that's weird."

by Aaron R. Wunderlich, John Raymond September 27, 2003