I had never heard the expression and made the awful mistake of looking up the verb
to twerk in the so-called Urban Dictionary. Here is what I found:
The rhythmic gyrating of the lower fleshy extremities in a lascivious manner with the intent to elicit sexual arousal or laughter in ones intended audience.
I found the missing apostrophe extremely offensive, and the video was very nearly as bad. I am not going to link to it directly, in case anyone here has neglected to block their children's access to the forums. But you can find it here:
http://www.urbandictionary.com/define.php?term=twerk
