My ex girlfriend or any other chick who isn't just ugly on the outside.
"Are you still with that one chick?"
"Nah, me and ol' c-face broke-up months ago."
Cunt face to put it bluntly! There are always times when a potent insult is required (typically in the absence of the insultee) but potent language can be a bit coarse on sensitive ears. Can be abbreviated to "C" if desired. Can be used to describe anyone who is generally unappealing - mentally, socially or physically.
Wommo:"That girl we were talkin to last night was an absolute C-Face!"
Jock:"Fucking oath! She was a dead-set C!"