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1. Fall asleep fast, as when one is extremely tired
   "after the long drive, we zonked out and slept for 10 hours";
   - zonk [informal]
    
2. Lose consciousness due to a sudden trauma, for example
   - pass out, black out, zonk [informal]

Derived forms: zonked out, zonking out, zonks out

Type of: change state, dope off, doze off, drift off, drop off, drowse off, fall asleep, flake out, nod off, turn