The Collaborative International Dictionary of English v.0.48:

Nuance \Nu`ance"\, n. [F.]
   1. A shade of difference; a delicate gradation.
      [1913 Webster]

   2. A small difference in meaning, significance, or
      expression.
      [PJC]

WordNet (r) 3.0 (2006):

nuance
    n 1: a subtle difference in meaning or opinion or attitude;
         "without understanding the finer nuances you can't enjoy
         the humor"; "don't argue about shades of meaning" [syn:
         nuance, nicety, shade, subtlety, refinement]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "nuance":
   allegory, allusion, amount, arcane meaning, assumption, caliber,
   coloration, compass, connotation, contradistinction, cut, dash,
   degree, delicacy, delicate distinction, demarcation, differentia,
   differential, differentiation, distinction, distinctiveness,
   distinguishment, division, extent, fine point, grade, hairline,
   hairsplitting, height, hint, implication, implied meaning, import,
   inference, innuendo, interval, intimation, ironic suggestion, leap,
   level, margin, mark, meaning, measure, metaphorical sense,
   microscopic distinction, narrow margin, nice distinction, nicety,
   notch, occult meaning, overtone, particle of difference, pas, peg,
   period, pitch, plane, plateau, point, point of difference,
   presumption, presupposition, proportion, range, ratio, reach,
   refinement, remove, round, rung, scale, scope, segregation,
   separation, shade, shade of difference, shadow, soupcon, space,
   stair, standard, step, stint, subsense, subsidiary sense,
   subtle distinction, subtlety, suggestion, supposition, suspicion,
   symbolism, tinge, touch, tread, trichoschistism, undercurrent,
   undermeaning, undertone, wide margin