The Collaborative International Dictionary of English v.0.48:

Uncompromising \Un*com"pro*mi`sing\, a.
   Not admitting of compromise; making no truce or concessions;
   obstinate; unyielding; inflexible. --
   Un*com"pro*mi`sing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

uncompromising
    adj 1: not making concessions; "took an uncompromising stance in
           the peace talks"; "uncompromising honesty" [syn:
           uncompromising, sturdy, inflexible] [ant:
           compromising, conciliatory, flexible]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "uncompromising":
   adamant, adamantine, cast-iron, dour, firm, flinty, fundamentalist,
   grim, hard, hard-core, hard-line, hidebound, immovable, immutable,
   implacable, impliable, inelastic, inexorable, inflexible,
   intransigent, iron, ironbound, ironclad, ironhanded,
   irreconcilable, muscle-bound, obdurate, obstinate, orthodox,
   procrustean, purist, puristic, puritan, puritanic, relentless,
   rigid, rigorist, rigoristic, rigorous, rock-ribbed, rockbound,
   single-minded, steely, stern, stiff, straightlaced, straitlaced,
   stubborn, unaffected, unalterable, unbending, unchangeable,
   uncompliant, ungiving, unmoved, unrelenting, unyielding