The writing below is from a book. Will you tell me what hissy means? I couldn't find it in my dictionaries.

The effect produced a sound not unlike that of a tire releasing air. It was awkward and strange-sounding, and elicited much more attention than the original lisp. I failed to se the hissy s as a solution.

Thank you,

Hissy = like an extended /s/ sound, sounding like a hiss (like the sound attributed to a snake or to pressurized air leaking from a tire).
And thanks again!