Rectitude (rkttd), n.
Etymology: [L. rectitudo, fr. rectus right, straight: cf. F. rectitude. See Right.]
1. Straightness. [R.] Johnson.
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.
3. Right judgment. [R.] Sir G. C. Lewis.
Syn. -- See Justice.
Shades of meaning
Fernald has no entry of its own for rectitude; he lists it under justice, virtue.
Where he writes about it:
Integrity, rectitude, right, righteousness and virtue denote conformity of personal conduct to the moral law, and thus necessarily include justice, which is giving others that which is their due. — from justice
Rectitude and righteousness denote conformity to the standard of right, whether in heart or act; righteousness is used especially in the religious sense. — from virtue