lour in WordNet English dictionary

1. look angry or sullen, wrinkle one's forehead, as if to signal disapproval
   frown  glower  lour  lower 
   
2. make lower or quieter
   "turn down the volume of a radio"
   turn down  lower  lour 
   
3. set lower
   "lower a rating"; "lower expectations"
   lower  lour