unattainable

adj.

达不到的，无法取得的；可望而不可即；

1. He always has unattainable goals in his mind.
   他的脑子里总是想一些高不可攀的目标。
2. In my opinion that is unattainable and unrealistic.
   我觉得那是难达到的和不实际的。

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Liebeskind DS & Kasner SE.Neuroprotection for ischemic stroke: an unattainable goal? CNS Drugs 15: 165−174
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