Synonyms for Reserved (same or very similar meaning)
WordNet sense 1 (reserved in advance):
engaged
WordNet sense 2 (tending to reserve or introspection):
withdrawn
WordNet sense 3 (showing modest reserve):
diffident
WordNet sense 4 (remote in manner):
aloof, distant
WordNet sense 5 (cool and formal in manner):
restrained, reticent, unemotional
From the ODE community, based on WordNet
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