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

• ground rule
• ground sloth
• ground snake
• ground squirrel
• ground state
• ground stroke
• ground substance
• ground swell
• ground tackle
• ground water
• ground wave
• ground zero
• ground-controlled approach
• ground-effect machine
• ground-emplaced mine
• ground-floor
• ground-hugging
• ground-service crew
• ground-shaker
• groundball
• groundberry
• groundbreaker
• groundbreaking
• groundbreaking ceremony
• groundcover