1. Having been flattened
   - planate

1. Make flat or flatter
   "flatten a road"; "flatten your stomach with these exercises" 
2. Become flat or flatter
   "The landscape flattened"
   - flatten out 
3. Lower the pitch of (musical notes)
   - drop

See also: planar, two-dimensional

Type of: alter, change, change form, change shape, deform, form, modify, shape

Antonym: sharpen

• antipodal opposition
• antipode
• antipodean
• antipodes
• antipollution
• antipope
• antiproton
• antiprotozoal
• antiprotozoal drug
• antipruritic
• antipsychotic
• antipsychotic agent
• antipsychotic drug
• antipyresis
• antipyretic
• antiquarian
• antiquarianism
• antiquark
• antiquary
• antiquate
• antiquated
• antique
• antiquity
• antiredeposition
• Antirrhinum