sleep like a log
Also, sleep like a top. Sleep very soundly, as in I slept like a log, or She said she slept like a top. Both of these similes transfer the immobility of an object to that of a person who is sound asleep (since a top spinning quickly looks immobile). The first dates from the late 1600s; the variant is newer.
Words nearby sleep like a log
sleep apnoea, sleep around, sleep hygiene, sleep in, sleep learning, sleep like a log, sleep movement, sleep off, sleep on something, sleep out, sleep over
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.