1. 先行，先走一步：
例句: You go ahead and tell him that I'm coming.
你先行一步，告诉他我随后就到。
2. 急不可待地去做；毫不犹豫地去做：
例句: The teacher told the students not to go out of yet, but Tom went ahead and left the room.
老师告诉学生们不要走出教室，可是汤姆急不可待地离开了房间。
3. 进行，进展；继续(做某事)：
例句: After the rain stopped, the men went ahead with their work of digging up the street.
雨停后，他们继续在街上挖掘。
4. 说吧，开始吧，开始(做某事)：
例句: “May I start?”“Yes, go ahead.”
“我可以开始了吗?”“可以，开始吧。”
5. 取得进展，取得进步：
例句: Is your work going ahead now that the workers have arrived?
既然工人们都到了，你的工程有进展吗?
6. [口语]擅自行事；独自行动：
例句: I warned her not to do that but she went ahead and did that.
我告诫她不那样做，但她不听还是那样做了。
7. 先走，行进在前面
8. (继续)前进
9. 着手
10. [用作祈使句]开始；进行；往下说
11. 进展
参考资料：http://dict.youdao.com/search?q=go+ahead&btnindex=%E6%90%9C+%E7%B4%A2&ue=utf8&keyfrom=dict.index