She's got a face like a slapped horse

I heard this in a movie from England. "She has a face like a slapped horse." What does it mean? Is it common?
Thanks.

I have never heard the expression (in the U.S.) but I love it. Here's my guess: "Horse-faced" means a long, homely face. So if the horse was slapped, it would look even worse.

Hmmm. The way in which it was said was more like "she's looking like a slapped horse at the moment". Not always, just right now. A mood. Meaning?...