有人揮手說「走吧」
這一支把「往前走」當成一個可以被給、被拿的東西：許可本身。
noun · B2
Permission to start doing something, given by the person or group with the power to decide: you give someone the go-ahead, or you get the go-ahead from them.
許可
核心畫面
The word is the two-word phrase go ahead packed into a single unit, so the movement is still inside it: something was held back, and now it moves forward. Picture a hand you on. Sometimes the word names the wave itself — the moment permission arrives. Sometimes it describes the people who never wait for the wave. And in a game it names the score that carries your team out in front.
這個字可以想成把 go ahead（往前走）壓成一個單位，動作還留在裡面：原本被擋著，現在可以往前了。畫面是有人朝你…更多收起
這個字可以想成把 go ahead（往前走）壓成一個單位，動作還留在裡面：原本被擋著，現在可以往前了。畫面是有人朝你揮手說「走吧」。有時候這個字指那個揮手本身——許可到手的那一刻。有時候它形容那種不等人揮手、自己就先動的人或公司。而在球賽裡，它指把自家球隊帶到前面去的那一分。From the word’s history
The Wiktionary entry records go-ahead as a deverbal formation from the phrasal verb go ahead, which is why the forward movement of the phrase is still felt in every use of the single word.
Wiktionary 記載 go-ahead 是從動詞片語 go ahead 轉成名詞／形容詞來的。這正好說明為什麼每一個用法裡都還聽得到「往前走」這個動作。
Wiktionary entry for go-ahead (kaikki extract, source_ref kaikki:3f6f69a190036ae4:971647804): "Deverbal from go ahead."
Three branches
不等人揮手就先動的作風
同樣是往前走，但這裡不是拿到許可的那一刻，而是一種長期的姿態：這家公司、這個人總是自己先動。
adjective · C1
Willing to try new methods and new ideas, and expected to do well because of it — used about a company, a school, a team, or the person running one; it can also describe someone who is energetic and keeps pushing forward.
有衝勁的
把比分帶到前面的那一球
這一支抓住的是 ahead 那一半：不是「開始」，而是「走到前面去」。在記分板上，那就是領先易主的那一分。
adjective · C1
In sports reporting, used about the run, goal or point that puts your team in front — the score that changes who is leading.
超前的