1. Having great weight.
  2. Having a high specific gravity. Having great weight in proportion to bulk.
  3. Difficult to bear. Often causing or characterized by severe pain or suffering.
  4. Of weighty import.
  5. Characterized by depth or intensity.
  6. Borne down by something oppressive.
  7. Slow or dull from loss of vitality or resiliency.
  8. Lacking sparkle or vivacity. Lacking mirth or gaiety.
  9. Dulled with weariness.
  10. Very rich and hard to digest.
  11. Relating to theatrical parts of a grave or somber nature.

The emotion of Heaviness is found in the Triple Heater meridian in the Fire element.

Definition from Dictionary by Merriam-Webster.