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Comprehensive
Dictionary Suite
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impossibly to a degree that causes difficulty or makes a solution unattainable. [1/3 definitions]
tantalize to tease or torment with the sight or prospect of something desirable but unattainable.
wild-goose chase the futile pursuit of something unattainable or nonexistent.
will-o'-the-wisp a false or unattainable hope or goal that leads one on. [1/2 definitions]