1. A change downward
   "There was a gradual lessening of tension in the room";
   - decrease, drop-off

1. Become reduced in amount, level, intensity, or value
   "The amount of homework lessened towards the end of the semester";
   - decrease, diminish, fall, come down, go down, sink, dent
    
2. Make become smaller
   "The distance lessened between the two cars";
   - decrease, minify
    
3. Wear off or die down
   "The pain lessened";
   - subside

Derived forms: lessenings

Type of: alter, alteration, change, change magnitude, modification, modify, weaken

Encyclopedia: Lessen