Definitions:

1. A ditch with a wall on its inner side below ground level, forming a boundary to a park or garden without interrupting the view. NOUN
   • At the edge of the garden, a ha-ha allows you to look directly out over the outer park and its fine trees.
2. Used to represent laughter or amusement. NOUN
   • 'Oh ha ha, very funny,' I said.

Synonyms:

• haw-haw
• hee-haw
• horselaugh
• sunk fence