Think of an animal crossing a dark yard: slow, low, almost silent, stopping and starting, with its eyes and ears never resting. It is not going anywhere in particular — it is covering the whole place — and it is doing that because it wants to find something. Prowl holds the movement and the reason together in one word. That is why the same picture still works when a person goes quietly round a shop, a room or a street, and why the noun uses feel like hunting even when nobody is hunting anything.
From the picture
把這種走法變成一段狀態或一趟行動（名詞）
名詞這一組沒有換畫面，只是換了拍攝角度：動詞拍的是「正在走」，名詞把同一件事框起來，變成「現在處於這個狀態」或「出去繞的這一趟」。所以前面配 be（be on the prowl）時是狀態，配 a／go for（go for a prowl）時就是一趟可以數的行動。
noun · B2
If an animal is on the prowl, it is out hunting — already moving quietly around an area, looking for food.
在獵食中
verb · B2
If an animal prowls, it moves around a place slowly and quietly, watching and listening the whole time, usually because it is hunting for food.
潛行
verb · B2
If a person prowls, they move slowly and quietly around a place, watching everything. It is used especially when someone is searching for something, when they may be up to something criminal, or when they are too restless to sit still.
潛行徘徊