(a.) Not flinching or shrinking; unyielding.

assiduous balanced calm constant continuing cool coolheaded diligent dogged enduring faithful fast fiducial firm firm as Gibraltar immutable imperturbable implacable in equilibrium inalterable indefatigable indomitable industrious inexcitable insistent invincible lasting loyal merciless mortal nerveless never-tiring obstinate patient patient as Job permanent perseverant persevering persistent persisting pertinacious plodding plugging predictable preoccupied rapt relaxed relentless reliable resolute rock-steady ruthless secure sedulous single-minded sleepless slogging solid sound stable steadfast steady steady-handed steady-nerved steel-nerved stick-at-nothing strong-nerved stubborn substantial tenacious tireless unabashed unabating unappalled unappeasable unawed unblenching unblinking unconquerable uncowed uncringing undaunted undiscouraged undismayed undrooping unfailing unfaltering unflagging unflappable unhesitant unhesitating unintermitting uninterrupted unintimidated unnervous unnodding unquivering unrelaxing unrelenting unremitting unshakable unshaken unshaky unshrinking unsleeping unstrained unswerving untiring untremulous unwavering unwearied unwearying unwinking unyielding utterly attentive weariless well-balanced without a tremor without nerves