lighten in WordNet English dictionary

1. make lighter or brighter
   "The paint will brighten the room"
   brighten  lighten up  lighten 
   
2. become more cheerful
   "after a glass of wine, he lightened up a bit"
   lighten  lighten up  buoy up 
   
3. make more cheerful
   "the conversation lightened me up a bit"
   lighten  lighten up  buoy up 
   
4. become lighter
   "The room lightened up"
   lighten  lighten up 
   
5. alleviate or remove (pressure or stress) or make less oppressive
   "relieve the pressure and the stress"; "lighten the burden of caring for her elderly parents"
   relieve  lighten 
   
6. reduce the weight on; make lighter
   "she lightened the load on the tired donkey"
   lighten