What is it?
A Disco Era swing-related dance that originated in New York around 1975. Imagine a 6 count swing at twice the speed (the timing goes "and-one--two--three"). It can be danced to disco music, as well as many post-70's pop songs and cha-chas.

Hustle is not an actual swing dance: In swing, the strongest musical accent is on every even dance count, with a lighter accent on most odd counts; In Hustle, the musical accent is on every dance count.

Swing
1 2 3& 4 5 6 7& 8
R S t-p S B S t-p S

Hustle
&1 2 3 4
a-1 2 3

There is also a 70's line dance called the Hustle.