Meaning of space cadet

space' cadet"

Pronunciation: [key]
— Slang. Slang.
  1. a person who appears to be in his or her own world or out of touch with reality.
  2. a person who behaves oddly or seems stupefied or remote because of the influence of drugs; druggie.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.