His teachers have all gone home for the weekend, so they won't be able to give me an idea of his intent until Monday, but right now he is watching TV and bouncing around excited while holding only his right hand level with his head, out to his right side, with fingers completely extended, and rotating his wrist so that his palm is alternating,twisting front to back, front to back,front to back. He "stims" on a regular basis (hands flapping in excitement) but this appears to be different than that, and much more deliberate. Does anyone have any idea what sign this might supposed to be? I can't seem to describe it in a way for Google to help me in the right direction. Unfortunately my own sign knowledge is very limited (mom, dad, eat, more, juice, pants, shoes, and a few others)

Any help at all would be most appreciated!

Edit: For those asking he was watching Super Simple Songs: Over the Deep Blue Sea on tv.

Final Edit: A couple people suggested that he was saying "yay" but only using one hand instead of two, so I watched a couple videos of the sign for yay and I now absolutely believe that he has been saying "Yay" but with only one hand.

Thank you so much!!