Literally, "bitch brat". A young girl who acts sassy and provocative towards adults in a sexually charged manner.
Typical attributes include smug or naughty expressions, a mocking laugh, a single fang, twintails, short shorts, miniskirts, exposed midriff, etc. May be an oppai loli.
Not to be confused with erogaki ("erotic brat") who is sexually forward or seductive without being sassy, or kusogaki ("shitty brat") who is sassy without a sexual undertone.