showing a tendency or inclination to be uncommunicative or reserved in speech, reluctant to reveal one's feelings or thoughts and choosing instead to remain silent;
e.g. He has chosen to remain reticent on this matter to avoid showing bias.
(adjective)
marked by restraint in presentation, appearance, or expression, not extravagant or excessive;
e.g. The room's furnishings were reticent but elegant.
(adjective)
reluctant, generally unwilling or hesitant about something;
e.g. I am reticent to share my true opinion for fear of offending anyone.