To engage in futile and pointless efforts; to attempt the impossible, like trying to carve ice into food or cook gravel into a meal.
做任何事情都应该脚踏实地，空想而“镂冰炊砾”是不会成功的。
When undertaking any task, one should be practical and grounded; merely daydreaming and engaging in futile efforts will not lead to success.
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