1. With no problems or difficulties
   "put the plans into effect quickly and smoothly"
   - swimmingly 
2. In a smooth and diplomatic manner
   "'And now,' he said smoothly, 'we will continue the conversation'"

See also: smooth

• unbounded
• unbounded interval
• unboundedness
• unbowed
• unbox
• unbrace
• unbraced
• unbraid
• unbrainwashed
• unbranched
• unbranching
• unbranded
• unbreakable
• unbreakableness
• unbridgeable
• unbridle
• unbridled
• unbroken
• unbrushed
• unbuckle
• unbundle
• unburden
• unburdened
• unburied
• unburned