zonk out

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

v 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

v lose consciousness due to a sudden trauma, for example

black out, pass out
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

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