up on something, be

up on something, be idiom
Be well informed or up-to-date about something, as in I'm not up on the latest models of cars. [Colloquial]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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