Locking (originally Campbellocking) is a style of funk dance, which is today also associated with hip hop. The name is based on the concept of locking movements, which basically means freezing from a fast movement and “locking” in a certain position, holding that position for a short while and then continuing in the same speed as before.
It relies on fast and distinct arm and hand movements combined with more relaxed hips and legs. The movements are generally large and exaggerated, and often very rhythmic and tightly synced with the music.
Explanation supplied courtesy of http://en.wikipedia.org/