1To begin speaking about something one had been silent on; to bring up a topic or opinion.
彼はなかなか本音を言い出せなかった。
He couldn't bring himself to say what he really thought.
息子が急に留学したいと言い出した。
My son suddenly said he wanted to study abroad.
会議で誰かがこの問題を言い出すのを待っていた。
I was waiting for someone to bring up this issue at the meeting.
言いにくいことを言い出す勇気が必要だ。
It takes courage to bring up something hard to say.
2To be the one who first voices an idea or proposal, ahead of others.
この企画は彼が最初に言い出したことだ。
He was the first one to propose this project.
「みんなで旅行に行こう」と言い出したのは田中さんだった。
It was Tanaka who first suggested, "Let's all go on a trip together."