What is horsin?

acting wild in the manner a horse would

did you see jess last night? she was really horsin' it up!

horsin - meme gif

a term for bangin hard, or riding em rough

I was horsin the shit out of your mom last night.

To do something retarded, to not think, to be an overall oblivious person to any situation, and someone that usually has issues paying attention.

Robinson stop horsin or you will actually break your wrist.