I thought long and hard about what to write here, in the end I went for a word for word translation of "as a mirror, as they speak" and was amazed when I got the green tick. These random sentences are great, really make me stop and concentrate on the words.
A basic Google search shows this is more of an English expression than a Portuguese one. Here's one of the examples I got, with corresponding context: "The sun is low in the sky and the sea is calm. Like a mirror as they say."
This saying appears to be an idiom saying. Can't quite put my finger on it. It's like if someone asked you, "How do I look?", then they answer could be, like a mirror. I don't know maybe I'm wrong about this.