Backpfeifengesicht (roughly, "BACK-fifengehzeekt") is a German word.

German words can be so wonderful, expressing depths and nuances of emotion in single words.

Backpfeifengesicht. A face in need of a slap.

You know it when you see it.

I mean, c'mon.  You...KNOW IT...when you see it.  Downturned lips from a lifetime of pouting about this or that.  Weak cheeks and chin.  Kind of amorphous features that simply shout, "Of, ffs, just slap me!"