Bitch mode is a mode you go into when you are being a bitch. Getting rejected by multiple girls or gettin outdrinkin by a beast may cause you to go into this embarresing state of mind. Those who frequently tend to go into bitch mode are the kids that are so skinny they have indents in their chest.
The opposite of bitch mode is beast mode
Gordy: Hey man watch me hit this blunt (hits it once, chiefs, throws up, then goes into bitch mode
Beast and his followers: hahahaha wow wat a BITCH