Simply what u say if u can remember a woman by how she looks but u cant remember her name.
When it is the same situation but with a man it is simply then "what's HIS face"....
a pronoun with similar usage to she or her; a great pen name if you write for eHow.com
Susan (wife): My sister's friends Anna, Joanie, and Miriam might be meeting us all at Applebee's tonight to use up that giftcard, too.
Ron (husband): Don't tell me fucking whatsherface is coming. No, no, no. This is bullshit. It's going to be like work. I hate this. I don't think I wanna go.