break out

break out（战争、打斗等不愉快事件）突然开始，爆发

【例句】

◆ The Second World War broke out  in September 1939．二战爆发于1939年9月。

◆ We watched, amazed as fire broke out on the outside of the spaceship as the earth's gravity increased．我们惊奇地看着，随着地球的引力增加，宇宙飞船的外层起火了。（人教版，必修③，Unit 4）