WordWeb Online

1. The property of being comparatively great in weight
   "the heaviness of lead";
   - weightiness
    
2. Persisting sadness
   "nothing lifted the heaviness of her heart after her loss"
    
3. An oppressive quality that is laborious and solemn and lacks grace or fluency
   "his lectures tend to heaviness and repetition";
   - ponderousness
    
4. Used of a line or mark
   - thickness
    
5. Unwelcome burdensome difficulty
   - burdensomeness, onerousness, oppressiveness

Type of: broadness, difficultness, difficulty, fix [informal], hole [informal], jam [informal], kettle of fish [informal], mess [informal], muddle [informal], pickle [informal], sadness, unhappiness, uninterestingness, weight, wideness

Antonym: lightness