Verb
(intransitive) To attack imaginary enemies.
(intransitive, by extension) To go on a wild-goose chase; to persistently engage in a futile activity.
Source: en.wiktionary.orgCome! Let us lay a lance in rest, And tilt at windmills under a wild sky! John Galsworthy
I don't take on a fight just for a fight. I don't tilt at windmills. Carly Fiorina
Come! Let us lay a lance in rest, And tilt at windmills under a wild sky! For who would live so petty and unblest That dare not tilt at something ere he die; Rather than, screened by safe majority, Preserve his little life to little end, And never raise a rebel cry! John Galsworthy