Ha-ha (noun)

1. A sunken fence or wall designed to prevent cattle or other animals from crossing a boundary.
2. A type of garden feature which is a sunken fence or a type of ditch or trench that is dug in a garden or a park.

Origin:

17th century, probably from the exclamation of surprise or pleasure.

Examples:

1. He built a ha-ha to keep the cows from wandering into the garden.
2. The ha-ha was a popular feature in 18th-century landscape gardens.
3. The ha-ha is a hidden barrier that creates the illusion of an open landscape.
4. The ha-ha was a great way to keep the deer out of the garden.
5. The ha-ha is a trench-like feature that stops livestock entering the garden without disrupting the view.