zonk out

/zɔŋk aʊt/

When you zonk out, you fall asleep suddenly. You may have seen babies be wide awake one minute and then zonk out the next.

A college student who was awake all night writing a paper might zonk out, and a toddler who refused to take an afternoon nap will usually zonk out at bedtime. You can also use the informal phrase to describe what happens when someone faints or is knocked unconscious. The word zonk became a popular slang term for "hit hard" in the 1950s, probably because the word sounds like the action of banging someone over the head.

Definitions of zonk out

1. verb

   fall asleep fast, as when one is extremely tired
   type of:

   dope off, doze off, drift off, drop off, drowse off, fall asleep, flake out, nod off

   change from a waking to a sleeping state
2. verb

   lose consciousness due to a sudden trauma, for example
   synonyms: black out, pass out

   types:

   conk, faint, pass out, swoon

   pass out from weakness, physical or emotional distress due to a loss of blood supply to the brain

   type of:

   change state, turn

   undergo a transformation or a change of position or action