ha-ha vs sunk fence

ha-ha and sunk fence both are nouns.

Word	Noun	Adjective	Verb	Adverb
ha-ha	Yes	No	No	No
sunk fence	Yes	No	No	No

As nouns, ha-ha and sunk fence are synonyms defined as:

ha-ha and sunk fence: a ditch with one side being a retaining wall; used to divide lands without defacing the landscape

Other synonyms of ha-ha include haw-haw.

ha-ha (noun)	sunk fence (noun)
a ditch with one side being a retaining wall; used to divide lands without defacing the landscape	a ditch with one side being a retaining wall; used to divide lands without defacing the landscape
a loud laugh that sounds like a horse neighing