vainly
adv. 徒劳地；无益地；枉然地
例句
He shouted after them, vainly trying to attract their attention.
他在他们的后面高喊，想引起他们的注意，却是徒劳。
《牛津词典》
He hunted vainly through his pockets for a piece of paper.
他徒劳地摸索着自己的口袋想找到一张纸。
《柯林斯英汉双解大词典》
The criminals vainly sought concealment from the searchlight.
罪犯们试图躲开探照灯光，纯属徒劳。
