Ratty can be a noun or adjective. If someone is acting like a rat, they are ratty, if someone always acts like a rat, they could be called ratty. Can also be referred to as spaz.
"That test was so ratty"
"Hey, ratty, are you coming tonight"
Pronounced: "Ih-sack". This person is the rattiest of them all. They never answer their texts and skip the gym all the time. Sometimes referred to as "spaz" or "rat" or "ratty".
"Isaac, you're a rat"
"Isaac, get on you dumb ass rat"