Step Out of Line: Origin and Meaning

To behave in an unacceptable or unexpected way.

In the military, soldiers had to follow strict rules to make sure they looked smart at all times. If they were standing or marching in a line and the line was not exactly straight, it was likely that one soldier had ‘stepped out of line’, making the whole unit seem untidy. According to the military, that particular soldier was behaving in an unacceptable way. The phrase is now used to describe any incorrect or unacceptable behaviour.

“Did you hear about Sam? He stepped out of line again on Monday and was fired from his job!”

“Jamie, you will not be allowed to go to the party on Saturday if you step out of line one more time this week!”

Tim: “I don’t know what to do about John. He arrives late to my lesson every day and always misbehaves. The other students are getting very annoyed.”
Jess: “Just tell him that he needs to start behaving correctly and if he steps out of line again, you will send him out of the class.”