flunk n. + Add to list US //ˈfɫəŋk// UK //flˈʌŋk// flunk Archaic Informal SynonymsAntonymsEtymology Synonyms bombfailfailing Antonyms passpassingOrigin Alteration of funk, or perhaps a blend of flinch + funk. Idioms1 entry01flunk outTo fail to finish school, or a given subject, program or course, due to academic shortcomings; i.e., to have too many flunking or failing grades (marks).