Verb (5-dan, す, transitive)
1. to begin to say; to start talking; to broach (a matter); to bring up; to come out with
彼はこちらが何か言い出すのを待っているような表情に見えた。He looked as if he was waiting for me to say something.
2. to be the first to say; to suggest (doing); to propose
そもそもこの勝負は、君が言い出したんだ。After all, you were the one who started this contest.