高珊的回答：

出发 they set off for the north yesterday. 激起，引起 set off a hydrogen bomb 出发还有同义词 set out start off start out get doing

shimmer的回答：

set off: 出发,侧重于去某个地方 例句与用法: if you want to catch that train we'd better set off for the station immediately. 你要是想赶上那班火车，咱们就最好马上动身去火车站。 they've set off on a journey round the world. 他们已经开始环游世界. set out: 出发，开始，侧重于开始做某事，还有规划，展现的意思 例句与用法: they succeeded in what they set out to do. 他们打算做的事已经做成了. set about: 开始,着手，与set out意思相近，但set out后加不定式，即set out to do sth,而set about后加 ing形式，即set about doing sth. 例句与用法: 1. you must set about your work at once. 你必须立即开始工作。 2. do you know how to set about going on this work? 你知道怎样着手进行这项工作吗？

何广燊的回答：

let's go set out start off start out get doing

刘青青的回答：

出发 leave set out start off departget going 用法详见http://www.iciba.com/search?s=%B3%F6%B7%A2

李亦凡的回答：

1.引起（事件，爆炸等）发生 2.使....开始做 3.（用比较的方法）使...更明显，衬托。