up on something, be
American Heritage Dictionary of Idioms:
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up on something, be
Be well informed or up-to-date about something, as in I'm not up on the latest models of cars. [Colloquial]
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American Heritage Dictionary of Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.
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