1. Changing for the worse
   "worried by the worsening storm"

1. Process of changing to an inferior state
   "The worsening of the products was evident after the company changed suppliers";
   - deterioration, decline in quality, declension [archaic]
    
2. Changing something with the result that it becomes worse
   "The worsening of weather conditions forced the cancellation of the outdoor event"

1. Grow worse
   "Conditions in the slum worsened";
   - decline
    
2. Make worse
   "This drug worsens the pain";
   - aggravate, exacerbate, exasperate

Type of: alter, change, change of state, change state, decline, diminution, modify, turn