Real Dictionary

discreet
adjective: If you are discreet, you are polite and careful in what you do or say, because you want to avoid embarrassing or offending someone.

discreet in American English
careful about what one says or does; prudent; esp., keeping silent or preserving confidences when necessary
adjective: judicious in one's conduct or speech, esp. with regard to respecting privacy or maintaining silence about something of a delicate nature; prudent; circumspect

discreet in British English
adjective: careful to avoid social embarrassment or distress, esp by keeping confidences secret; tactful