A throaty sound that imitates the heavy bass pounding that one would hear at a dance club or a strip joint, sometimes used along with suggestive hand motions to communicate a basic desire to mate.
It's encouraged to club dance while making the unsa unsa noise to show friends and onlookers how you would approach a prospective female.
It's also a noise that you can make to one of your friends after watching a hot chick walk by, and it would act much like a soft wolf whistle or a raised eyebrow.
*Hot girl walks by
Matt "unsa unsa"