Idioms and Phrases with up on something, be
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]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.