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slang Someone who is very stupid. Can you believe that dum-dum is still pushing the door marked "pull"?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
n. a stupid oaf; a dullard. Marvin is no dum-dum. He just looks that way.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.