upright, honest, just, conscientious, scrupulous, honorable mean having or showing a strict regard for what is morally right. upright implies a strict adherence to moral principles.

UPRIGHT definition: erect or vertical, as in position or posture. See examples of upright used in a sentence.

upright adjective (MORAL) honest, responsible, and moral: an upright young man (Definition of upright from the Cambridge Academic Content Dictionary © Cambridge University Press)

1. A perpendicular position; verticality. 2. Something, such as a goalpost, that stands upright. 3. An upright piano. 4. An upright bicycle.

Upright, erect, vertical, perpendicular imply that something is in the posture of being straight upward, not leaning. That which is upright is in a position corresponding to that of a person …

There are 39 meanings listed in OED's entry for the word upright, 12 of which are labelled obsolete. See ‘Meaning & use’ for definitions, usage, and quotation evidence.

If you are sitting or standing upright, you are sitting or standing with your back straight, rather than bending or lying down.