Wiktionary
tilt at windmills
alt. 1 (context intransitive English) To attack imaginary enemies. 2 (context intransitive idiomatic English) To go on a wild-goose chase; to persistently engage in a futile activity. vb. 1 (context intransitive English) To attack imaginary enemies. 2 (context intransitive idiomatic English) To go on a wild-goose chase; to persistently engage in a futile activity.
Usage examples of "tilt at windmills".
I was an idealistic kid and I wanted to go and tilt at windmills to protect her.
What the devil did he care if the woman was idiot enough to think she could tilt at windmills?