The Collaborative International Dictionary of English v.0.48:

Downright \Down"right`\, a.
   1. Plain; direct; forthright; unceremonious; blunt; positive;
      as, he spoke in his downright way.
      [1913 Webster]

            A man of plain, downright character.  --Sir W.
                                                  Scott.
      [1913 Webster]

   2. Open; artless; undisguised; absolute; unmixed; as,
      downright atheism.

   Syn: honest-to-goodness. [1913 Webster]

              The downright impossibilities charged upon it.
                                                  --South.
        [1913 Webster]

              Gloomy fancies which in her amounted to downright
              insanity.                           --Prescott.
        -- Down"right`ly, adv. -- Down"right`ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

downrightness
    n 1: the quality of being direct and straightforward; "what some
         people take for rudeness is really straightforwardness"
         [syn: downrightness, straightforwardness]