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Sl. to refuse to talk. Jill dummied up when they got her into the station. John dummied up right away when the police arrived.
1. To refuse to talk or to stop talking suddenly: I was told to dummy up until my lawyer arrived.
2. To make a model of some publication or page layout: Dummy up the first page and I'll look at it. If you're finished proofreading the article, dummy it up.
in. to refuse to talk. (see also clam up.) Rocko dummied up right away. He’s a real thoroughbred.