catch some z's
Take a nap, go to sleep, as in I stayed up all night studying so I'd better catch some z's. This term alludes to the buzzing sound of snoring. [Slang; second half of 1900s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.