What exactly does it mean to look "British"?

It's not a compliment or an insult, just a statement of opinion or observation.

My mom gets this a lot too since she is half-British. She's fair and has blue eyes, maybe that's what the majority of British people look like. But that could describe people from quite a few other countries too. It seems like a huge generalization, though.

Well England gets less sun the other parts of the world, especially London so British are usually pale. They usually have strong jaw lines and fine features (slim bridges of noses, aquiline noses) smaller frames than say someone who is Russian or Dutch. Their teeth are not a white or straight as say an American's because of the lack of VITAMIN D, and they drink a ton of tea with everything so it stains their teeth. They're fair-skinned for the most part. If that makes any sense.

It would mean something different for everyone. My Dad and I will say that someone looks like a pom if they have bad teeth and pasty skin. Obviously not all British people have bad teeth and pasty skin...I dated a British guy who was built like a Ken doll. But the majority that you see on reality TV shows or backpacking have really really bad teeth. I heard that it's because there's not as much awareness in Britain about dental hygeine, and that it's also more expensive. A friend of mine is British and he looks like he's got about twenty extra teeth in his top jaw alone.

A lot of people will say this if they think you look like someone of the British royal family. One friend of mine always getting this said to him and it is because he looks like Prince Charles.