You can think of a gum tree as a very tall trunk that leaks something sticky and carries leaves with a sharp, cool smell. Two things about it stay with people: it is high, and you cannot easily get down from it once you are up there.
「gum tree」可以想成一棵又高又直的樹。樹皮被割開就滲出黏黏的膠，名字裡的 gum 就是從這裡來的。葉子搓破以後有一股很衝、很清涼的味道，那就是尤加利精油。這棵樹留給人的印象有兩個：一是高，二是爬上去以後不好下來。第一個印象撐起它的本義，第二個印象撐起那句英式俚語。