That could mean getting gray hair.

那可能意味着头发变白了。

Some people think that if you've got gray hair, you're not all there.

有些人认为，如果你有一头白发，那你就不是白发了。

So, when you get older, you often get gray hair; it's what we call your hair when it gets white.

所以，当你年纪大了， 你的头发往往会变白；当它变白时， 这就是我们所说的头发。