Definitions of restrained:

• adjective:   under restraint
• adjective:   not showy or obtrusive
• adjective:   marked by avoidance of extravagance or extremes

  Example: "Restrained in his response"

• adjective:   prudent
• adjective:   cool and formal in manner
• adjective:   free from ostentation or pretension

  Example: "The restrained elegance of the room"