Ha ha or ha ha ha is used in writing to represent the sound that people make when they laugh. I dropped my bag at the officer's feet. The bank notes fell out. `Ha ha ha!' he laughed. `Got no money, uh?'
People sometimes say `ha ha' to show that they are not amused by what you have said, or do not believe it. He said `vegetarians unite', and I looked at him and said `yeah, ha ha'
The haha or sunken fence is a type of boundary to a garden, pleasure-ground, or park, designed not to interrupt the view and to be invisible until closely approached