WordWeb Online

1. Cool and formal in manner
   - reticent, unemotional
    
2. Under restraint
    
3. Marked by avoidance of extravagance or extremes
   "restrained in his response";
   - moderate
    
4. Not showy or obtrusive
   "clothes in restrained good taste";
   - quiet
    
5. Prudent
   "restrained optimism";
   - guarded

1. Remain under control
   "restrain your temper";
   - keep, keep back, hold back
    
2. Place limits on (extent or access)
   "restrain the use of this parking lot";
   - restrict, trammel, limit, bound, confine, throttle
    
3. Limit to within certain bounds; physically prevent from moving
   - confine, hold
    
4. Limit or hold back; keep within a small range
   - encumber, cumber [archaic], constrain
    
5. To compel or deter by or as if by threats
   - intimidate

See also: cautious, close, controlled, inhibited, low-key, low-keyed, reserved, subdued, temperate, undemonstrative, unexpansive, unostentatious, unpretending, unpretentious

Type of: bottle up, check, contain, control, curb, disable, discourage, disenable, frustrate, hold, hold in, incapacitate, inhibit, moderate, suppress

Antonym: unrestrained