The Collaborative International Dictionary of English v.0.48:

Offish \Off"ish\, a.
   Shy or distant in manner; aloof; stand-offish. [Colloq. U.S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

offish
    adj 1: lacking cordiality; unfriendly; "a standoffish manner"
           [syn: offish, standoffish]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "offish":
   Olympian, above all that, ailing, aloof, backward, bashful, blank,
   chilled, chilly, cold, constrained, cool, detached, discreet,
   distant, donsie, exclusive, expressionless, forbidding, frigid,
   frosty, guarded, icy, impassive, impersonal, inaccessible,
   indisposed, insociable, introverted, low, mean, modest, off-color,
   poorly, remote, removed, repressed, reserved, restrained, reticent,
   retiring, seclusive, shrinking, sickly, solitary, standoff,
   standoffish, subdued, suppressed, unaffable, unapproachable,
   unbending, uncongenial, undemonstrative, unexpansive, ungenial,
   withdrawn