Someone who is ratchet is someone who listens to rap junk, like Nikki Manaj, Lil Wayne, Drake, etc. Someone who is using slang terms like bae, doe, dat, bish, etc., a person who is wearing pounds of makeup just to go the freaking store.
DAMN THAT BISH RATCHET!!!!
You: Hey what's up ratchet girl?
Ratchet person: Nun u?
You: You* Nothing* uhhh.... Nothing much.
Ratchet person: I dun kno if my bae is comin ovr.
You: *FACEPALM*