[adj] prudent; "guarded optimism"
[adj] cool and formal in manner
[adj] free from ostentation or pretension; "the restrained elegance of the room"
[adj] not showy or obtrusive; "clothes in quiet good taste"
[adj] under restraint
[adj] marked by avoidance of extravagance or extremes; "moderate in his demands"; "restrained in his response"
bated, cautious, checked, close, confined, contained, curbed, discreet, guarded, low-key, low-keyed, moderate, modest, quiet, reserved, reticent, subdued, temperate, undemonstrative, unemotional, unexpansive, unostentatious, unpretentious