In a couple of Coldplay's songs, they use the phrase "Wait in line" one instance would be in the song "Parachutes" from the album Parachutes. What exactly does that mean?
Yes it is pretty straight forward I think. The girl is not into the guy so the guys says he'll wait for her, he will wait in line. Maybe she's with some one else at the moment so he waits patiently until it's his turn.
(without listening to the songs in question)
"Wait in line" basically means "Queue until it's your turn".
For example, you go into a bank and there are 10 people waiting in front of you all queuing to be served. So, you join the end of a queue ( or "line" ) and wait until it's your turn to be served.