1) An act or instance of this 2) Assumption 3) Audaciousness 4) Audacity 5) Brass neck 6) Brazen boldness 7) Cheek 8) Chutzpah 9) French word used in English 10) Insolent boldness 11) Presumption 12) Presumptuousness Found on https://www.crosswordclues.com/clue/effrontery
• (n.) Impudence or boldness in confronting or in transgressing the bounds of duty or decorum; insulting presumptuousness; shameless boldness; barefaced assurance. Found on http://thinkexist.com/dictionary/meaning/effrontery/
Ef·front'er·y noun ; plural Effronteries . [ French effronterie , from effronté shameless, from Latin effrons , - ontis , putting forth the forehead, i. e. , barefaced, shameless; ex + frons the forehead. See Front .] Impuden... Found on http://www.encyclo.co.uk/webster/E/12