cross a line(redirected from crossing a line)
cross a line
1. Of an action, to cross some threshold into unacceptable or inappropriate behavior. Speaking that rudely to your teacher definitely crosses a line.
2. To misbehave or do something unacceptable or inappropriate. When you spoke that rudely to your teacher, you definitely crossed a line.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.