Flunk \Flunk\ (fl[u^][ng]k), v. i. [imp. & p. p. {Flunked} (fl[u^][ng]kt); p. pr. & vb. n. {Flunking}.] [Cf. {Funk}.] To fail, as on a lesson; to back out, as from an undertaking, through fear. [1913 Webster]