Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Ha-ha \Ha-ha"\ (h[aum]*h[aum]"), n. [See Haw-haw.] A sunk fence; a fence, wall, or ditch, not visible till one is close upon it. [Written also haw-haw.]
Douglas Harper's Etymology Dictionary
also haha, used of laughter since ancient times; compare Old English ha ha, Greek ha ha, Latin hahae. A different attempt at representation is in py-hy (1580s).
Etymology 1 alt. An approximation of the sound of laughter. interj. An approximation of the sound of laughter. n. 1 A laugh. 2 Something funny; a joke. Etymology 2
alt. A ditch with one vertical side, acting as a sunken fence, designed to block the entry of animals into lawns and parks without breaking sightlines. n. A ditch with one vertical side, acting as a sunken fence, designed to block the entry of animals into lawns and parks without breaking sightlines.
A ha-ha is a recessed landscape design element that creates a vertical barrier while preserving an uninterrupted view of the landscape beyond.
The design includes a turfed incline which slopes downward to a sharply vertical face, typically a masonry retaining wall. Ha-has are used in landscape design to prevent access to a garden, for example by grazing livestock, without obstructing views. In security design, the element is used to deter vehicular access to a site while minimizing visual obstruction.
The name "ha-ha" may derive from the unexpected (i.e., amusing) moment of discovery when, on approach, the vertical drop suddenly becomes visible.
Usage examples of "ha-ha".
Just consider how well things had gone yesterday morning when Henry Patterson threw his control-freak hissy fit, ha-ha.
Glass photographs from its early glory days show an elaborate pile of building, recomplicated with trap-doors and hidden passages within, and topiary gardens and ha-has without.
It was weird and beautiful and exciting to be sitting out there listening to the bullbats squeak, waiting for people to ha-ha all at once on account of some poor sap getting a pie in the face, or yelp and squeal when the spaceships landed and let loose with a barrage of ray-guns.
Had I known the Duse was there, her poet chap might have found dangerous competition, ha-ha.
For him, it was impossible to celebrate with hoarse ha-has, like his cousins, the discomfiture of these women when they realized that they had wasted so many hours without accomplishing more than abundant drinking.
I spent half an hour over there and she put him down constantly, all these barbs and zingers, little ha-has at his expense.
She gestured out through the window, at the terrace of rosebushes and the garden beyond the ha-ha, the walls and trees and the avenue leading uphill to the stately home.