persistent Synonyms

pertinacious unrelenting tenacious relentless dogged unyielding lasting sustainable sustained substantial subacute stubborn strong-minded strong tight timeless unflinching unfailing undying undaunted unconquerable unbroken tolerant tireless stout stiff-necked stiff sedulous seamless scrappy robust rigid reverberatory retentive resolved resolute sempiternal sequential steady steadfast staying staunch stationary stable sound single-minded settled repetitive unremitting yearlong