The Collaborative International Dictionary of English v.0.48:

Unflinching \Unflinching\
   See flinching.

The Collaborative International Dictionary of English v.0.48:

Unflinching \Un*flinch"ing\, a.
   Not flinching or shrinking; unyielding. --
   Un*flinch"ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unflinching
    adj 1: not shrinking from danger [syn: unblinking,
           unflinching, unintimidated, unshrinking]

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "unflinching":
   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