Quick Springer

A person (typically male) who gets horny and aroused quickly at any little thing that they find sexually exciting.

“Are you already hard? I barely touched you.”
“Yeah sorry, I'm a quick springer.”

“She didn’t stop squirming during that hardcore bondage scene in the movie, I don’t know why because it was gruesome.”
“You didn’t know? Shes a quick springer and likes that type of stuff.”