An unavailing attempt to do something does not succeed.
例句
Efforts to reach the people named in the report proved unavailing...联系过报告中所提到的那些人，但都徒劳无功。He died after a brave but unavailing fight against a terminal illness.在与绝症进行了一番勇敢但却徒劳的抗争之后，他还是去世了。
英汉词典释义
adj.
徒劳的;无效的;无用的
All our protests were unavailing.我们的抗议全部无用。
英英词典释义
Adjective
1. producing no result or effect;
"a futile effort""the therapy was ineffectual""an otiose undertaking""an unavailing attempt"