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Synonyms for Discreet (same or very similar meaning)

WordNet sense 1 (unobtrusively perceptive and sympathetic):
discerning

WordNet sense 2 (having or showing a sense of what is fitting and considerate in dealing with others):
tactful

WordNet sense 3 (heedful of potential consequences):
circumspect

WordNet sense 4 (careful and sensible; marked by sound judgment):
prudent

WordNet sense 5 (free from ostentation or pretension):
restrained


From the ODE community, based on WordNetadd/edit