WordNet (r) 3.0 (2006):

low profile
    n 1: a state of low visibility in which public notice is
         avoided; "he was never one to keep a low profile"

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "low profile":
   blear, bleared, bleariness, bleary, blur, blurred, blurriness,
   blurry, confused, dark, darkness, defocus, dim, dimness, faint,
   faintness, feeble, feebleness, filminess, filmy, fogginess, foggy,
   fuzziness, fuzzy, half-seen, half-visibility, half-visible,
   haziness, hazy, ill-defined, inconspicuous, indefinite,
   indefiniteness, indistinct, indistinctness, indistinguishability,
   indistinguishable, merely glimpsed, mistiness, misty, obscure,
   obscurity, out of focus, pale, paleness, semivisibility,
   semivisible, shadowiness, shadowy, soft focus, uncertain,
   uncertainty, unclear, unclearness, undefined, unplain, unplainness,
   unrecognizable, vague, vague appearance, vagueness, weak,
   weakness