This is an ill-defined concept.
这是一个不确切的概念。
一个定义不明的概念；
If we think about it, wind chill is an ill-defined concept.
仔细想来，风寒是一个定义不清楚的概念。
So that's ill-defined and the same is true for the acceleration.
因此无法定义速度，加速度也是一样。
The boundary on the cold air side is often ill-defined, especially near the surface.
冷空气一侧的边界常常十分模糊，特别是在地表附近。
As we know design problems are ill defined.
正如我们所知道的，设计问题的界定是模糊的。
As we know design problems are ill defined.
正如我们所知道的，设计问题的界定是模糊的。
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