1) Aloof 2) Indrawn 3) Introvert 4) Recalled 5) Recluse 6) Reclusive 7) Reserved 8) Retired 9) Retracted 10) Shy 11) Suspended 12) Unsociable 13) Unsocial 1) Introverted 2) More than just reserved 3) Recluse 4) Reclusive 5) Reserved 6) Seeking solitude 7) Shrinking 8) Unsocial 9) Withdrawn from society 
• (p. p.) of Withdraw
[SAT terms] tending to reserve or introspection