One who deals with reality in a way consistent with being under the influence of (or "spaced out on") drugs.
A person in training to be a (generally military) astronaut, especially in science fiction.
One who forgets, daydreams, or otherwise is distracted from reality more often than most.
A person with a drug or alcohol addiction.
An absent-minded or vacuous person.
A person regarded with contempt; a loser.