This one has so many different names and clunk is not necessarily the most popular, it’s just the one my teacher uses. I’ve heard it called a flam and a slam as well.
Tip: Technically the one I’m demonstrating requires you to hit both the ball tap and heel tap at the exact same time. If they hit at slightly different times I would call that a clunk flam.
Clunk = clunk
Tap Dance Move Shown by Rod Howell