This is the point of contact from the coxix tho the anus of one's buttocks. As the buttocks can be spread apart, the contact forms a 'crease'. This crease in in one's buttocks is known as the 'Batty Crease'. It is a colloquialism that can be used as a noun or an adjective.
'You're a dirrrty battycrease bitch!'(in terms of adjective) 'Yo bitch's batty crease is masssive man!'(noun)
The point at which ones thighs meet at the back of the body, usually referred to as the buttocks. The "batty crease" is therefore the crack in ones buttocks
"That yattie over there, she got some big up battycrease. Me see it like the grand canyon, man."
Batty crease lips are dem lips that are dried up. The crusty lips that look like tiger bread. No one wants go near them because they look like a pensioners batty.
James says to Jordan;
Oi jord you got dem batty crease lips man. Get some vasoline on dat shit.