1. To become straight; to form into a line or row. The teacher waited for her students to come into line before they walked to the auditorium. The cars all came in line after the traffic merged into a single lane.

2. To conform, adhere to, or agree with that which is established or generally accepted, such as rules, beliefs, modes of behavior, etc. You might have some wild ideas for the future, but you'll never get anywhere in this business if you don't start coming into line with your boss's expectations. We all tend to have revolutionary ideals in our youth, but we usually come in line with the general populace as we grow older.