The term 'ratchet' has no less than two distinct meanings. As an adjective, it describes a person, usually a woman, or activity, who is out of hand, out of control, generally whack in some way, dirty, ghetto, unattractive, Crucian, or just generally disliked. As a verb, or a direct object ("do tha ratchet, yeah, do tha ratchet..."), the term serves to identify or describe the dance craze--and the movements associated herewith-- of the Ratchet.
A person, usually a woman, who is dirty, ghetto, unattractive, or just generally disliked.
"Man, did you see that chick?!"
"Oh, her? Yeah, man she's ratchet."