Advice as to what Snaking Head means

I had a wow moment over the weekend. When I got my horse a couple weeks ago, his previous owner sent along a big rubber ball with a handle. I've left this ball with him the entire time so as to create some 'normalcy' in the new home. I had not seen him touch or play with this ball until this weekend. Well, when he picks up his ball and throws it in the air, he "snakes" his head! I was very surprised to see the same movement that I thought was defiance or attitude when the whole time, maybe he just wants to play?! Anyway, thought it was curious enough to share.

I have a couple horses who are very sweet, but have onry tendencies.

Shooter, an 18 year old gelding, also snakes his head. He usually does it when he's not been ridden for a while, however... at feed time, our rescue horse Chance, also does it when he sees people coming with his food.

He loves feeding time, so I don't understand how the snaking could be a sign of displeasure or dominance.