The Collaborative International Dictionary of English v.0.48:

Rectitude \Rec"ti*tude\ (r?k"t?*t?d), n. [L. rectitudo, fr.
   rectus right, straight: cf. F. rectitude. See Right.]
   1. Straightness. [R.] --Johnson.
      [1913 Webster]

   2. Rightness of principle or practice; exact conformity to
      truth, or to the rules prescribed for moral conduct,
      either by divine or human laws; uprightness of mind;
      uprightness; integrity; honesty; justice.
      [1913 Webster]

   3. Right judgment. [R.] --Sir G. C. Lewis.
      [1913 Webster]

   Syn: See Justice.
        [1913 Webster]

WordNet (r) 3.0 (2006):

rectitude
    n 1: righteousness as a consequence of being honorable and
         honest [syn: uprightness, rectitude]