unavailing

Despite hours of effort, their attempts to fix the old radio proved unavailing.

用法提示：unavailing 作表语形容词，表示“徒劳的”。

His unavailing search for the missing key made him late for work.

用法提示：unavailing 作定语形容词，修饰 search，表示“毫无结果的”。

She knew that arguing with him would be unavailing, so she stayed silent.

用法提示：unavailing 作表语，说明争论是“无效的、徒劳的”。