Read between the lines

Meaning/Usage: To understand the underlying meaning of something that is not completely clear.

Explanation: There are no words between the lines. However, there are many written text like poetry, proverbs, or riddles that require you to understand more than what is written to completely understand it. This phrase became popular so people started using it to refer to understanding hidden meaning.

"If you read between the lines, you would have understood what he was implying."
"Steve isn't very good at reading between the lines. You have to tell him exactly what you want."
"Martha can read between the lines very well. She picks up on everything."

A: "Did you read chapter three for our English class?"
B: "Yeah. I think the author was indicating that he was supporting the war."
A: "Even though he said one thing, he meant another. You have to read between the lines to fully understand his stance."
B: "That might be true. I should go read it again."