folly āļāļ·āļāļāļ°āđāļĢ folly āļāļ·āļāļāļ°āđāļĢ A lack of good sense, understanding, or foresight.An act or instance of foolishness: regretted the follies of his youth. A costly undertaking having an absurd or ruinous outcome. An elaborate theatrical revue consisting of music, dance, and skits.Obsolete Perilously or criminally foolish action.Obsolete Evil; wickedness.Obsolete Lewdness; lasciviousness.