The circling hip action of Latin dance. It doesn't come from swinging the hip, but from alternately bending and straightening the knees – the hip merely follows.
This is where nearly every beginner gets stuck: they \"do\" the hip – and end up looking stiff and staged. The mechanism runs the other way. Shift your weight onto one leg and straighten that knee fully; the hip on that side lifts by itself, while the other knee stays soft and that hip drops. The sideways tilt only becomes a circle once you carry the weight transfer round rather than in a straight line. The finishing touch is called settle: the hip arrives a fraction after the foot, not with it – that delay gives rumba and cha-cha-cha their drawn-out character. And a point that often gets lost: in this movement the hip joint works harder and longer than the knee or ankle. Warm it up before you set it circling.