noun, noun or participle which takes 'suru'
Baseball term: a strikeout where the batter swings and misses. Literally 'swing-and-miss strikeout'.
See also: 三振
彼は空振り三振に倒れた。
He went down on a swinging strikeout.
noun
repeated failures; vain attempts
Idiomatic use: trying hard several times but failing each time, like swinging and missing repeatedly. Often used with 〜に終わる.
彼の努力は空振り三振に終わった。
His efforts ended in repeated failures.