WordNet (r) 3.0 (2006):

schizoid
    adj 1: of or relating to or characteristic of schizophrenia
           [syn: schizoid, schizophrenic]
    2: marked by withdrawal and inability to form close
       relationships
    n 1: characterized by symptoms similar to but less severe than
         schizophrenia [syn: schizotypal personality, schizoid]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "schizoid":
   alcoholic, alternating personality, ambivert,
   antisocial personality, brain-damaged, brain-injured, catatoniac,
   catatonic, certifiable, certifiable case, choleric, cycloid,
   cyclothyme, cyclothymic, disordered personality, disturbed,
   disturbed personality, double personality, drug user,
   dual personality, ectomorph, emotionally unstable personality,
   endomorph, escapist, extrovert, hostile personality, hypochondriac,
   hypochondriast, idiot, imaginary invalid, immature personality,
   inadequate personality, inferior personality, introvert,
   malade imaginaire, maladjusted personality, manic-depressive,
   melancholic, mental, mental case, mentally defective personality,
   mentally ill, mentally sick, mesomorph, moral insanity,
   multiple personality, neuropath, neurotic, neurotic personality,
   paranoiac, paranoid, paranoid personality, perverse personality,
   phlegmatic, psycho, psychoneurotic, psychopath, psychopathic,
   psychopathic case, psychopathic personality, psychotic,
   psychotic personality, sanguine, schiz, schizo,
   schizoid personality, schizophrenic, schizothyme, schizy,
   seclusive personality, sexual psychopath, shut-in personality,
   sociopath, split personality, syntone, valetudinarian,
   valetudinary, weak personality