1. Confused or disoriented as if intoxicated through taking a drug
   "After the long flight, he felt spaced-out and couldn't think clearly"
    
2. Stupefied by (or as if by) some narcotic drug
   "The spaced-out look in his eyes suggested he wasn't fully present";
   - spacy [informal], spacey [informal]

See also: confused, fuddled, unconventional