What is this move in this kata?

Just so you know you are doing a back kick in the middle of that jump.

I use this for a number of applications, and have even seen many others some of which i can agree with.

The drop to the ground can represent a few things, one of which is that it represents what happends to your opponent.

Kata bunkai is not always what you are doing in some cases it is what your opponent is doing, or what is happening to him.

The cresent kick in the second move can be utilized as a step off from the opponents knee then back kicking the person,

Although one that i often use is,

The open hand is a block, you then use the cresent kick into the opponents knee followed by the back kick, where the drop represents the opponent falling.

There is also another one where this is a really nasty throw.

This is one of my favorite kata, there are several nice aikido techniques that work great in bunkai for this kata

Btw you put this in the wrong catagory

I remember doing a similar move in one of my kata's. It's just a smooth, cool jump you do and while you're doing it, you grab the opponents head and smack it into your knee/shin/ankle.