From Longman Dictionary of Contemporary Englishthumb your nose at somebody/somethingthumb your nose at somebody/somethingREJECT/NOT ACCEPTto show that you do not respect rules, laws etc or you do not care what someone thinks of you a chance to thumb his nose at the college authorities → thumb
Examples from the Corpus
thumb your nose at somebody/something• So long as he had the support of Sir Rufus Stone, he could thumb his nose at Cotton.• Voters have thumbed their noses at it.• Voters here have always been drawn to against-the-grain outsiders who make a career of thumbing their noses at party traditionalists.• Judges who thumb their noses at presidents are thought to be good for democracy.• The protestors were denigrating the primary symbol of the ordained ministry, they claimed, and thumbing their noses at the Church.• Faubus had again thumbed his nose at the judiciary by refusing to appear.• This is yet another example of Republicans thumbing their nose at the poor. 