pertinacious (pur-tin-AY-shuhs) adjective 1. Holding resolutely to a purpose, belief, or opinion. 2. Stubbornly unyielding. [From Latin pertinac- pertinax, per- (thoroughly) + tenax (tenacious), from tenere (to hold).] Today's word in Visual Thesaurus: http://visualthesaurus.com/?w1=pertinacious... Sign in to see full entry.