Speak out of turn
Definition 1 of 1
Pro Tip 1/3Speak Without Permission
The phrase often relates to saying something in a discussion without waiting for your turn or permission. 
During the meeting, John began to speak out of turn and the manager had to remind him to wait his turn.
Pro Tip 2/3Impolite Connotation
Using this phrase can imply that someone's behavior is impolite or disrespectful. 
She was offended because he spoke out of turn, cutting off her sentence.
Pro Tip 3/3Inappropriate Content
It might also refer to saying something inappropriate or not suitable for the situation. 
I didn’t mean to speak out of turn by mentioning his financial issues at the party.