1. Not brought about by coercion or force
   - uncoerced, willing 
2. Not resulting from undue effort; not forced
   "a voice with a pleasingly unforced quality"
   - unstrained

See also: effortless, voluntary

• flare-up
• flaring
• flash
• flash butt welding
• flash camera
• flash in the pan
• flash lamp
• flash memory
• flash welding
• flash-forward
• flash-freeze
• flash-frozen
• flashback
• flashboard
• flashboarding
• flashbulb
• flashcard
• flasher
• flashflood
• flashgun
• flashily
• flashiness
• flashing
• flashlight
• flashlight battery