Vain, n. Vanity; emptiness; — now used only in the phrase in vain.
For vain. See In vain. Shak. — In vain, to no purpose; without effect; ineffectually. “ In vain doth valor bleed.” Milton. “ In vain they do worship me.” Matt. xv. 9. — To take the name of God in vain, to use the name of God with levity or profaneness.