To be without a solid foundation, lacking practical basis, or being unrealistic and vague; without a definite place or support.
这个新项目听起来很有趣，但计划书里细节模糊，让人感觉上不属天，下不着地，很难具体实施。
This new project sounds interesting, but the details in the proposal are vague, making it feel without a solid foundation and hard to implement concretely.
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