Synonyms for Withdrawn (same or very similar meaning)
WordNet sense 1 (withdrawn from society; seeking solitude):
recluse, reclusive
WordNet sense 2 (not seeking or given to association; being or living without companions):
unsocial
WordNet sense 3 (tending to reserve or introspection):
indrawn
WordNet sense 4 (marked by self-restraint and reticence):
reserved
From the ODE community, based on WordNet
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