Adjective

1. Extremely fatigued.

   After eighteen hours of proofreading, I was completely zonked.

2. Deeply asleep.

   I must have been really zonked. They said it took fifteen minutes to wake me up.

3. Drunk.
   • 1974, New York Magazine‎ (volume 7, number 27, July 1974)

     ...swingers in the audience were getting zonked on beer and fresh sea breezes and sound...

   • 2004, Ed Sanders, Tales of beatnik glory

     ...playing eight-ball while zonked, chugging beer with locals...