'To improve upon' definitions:

Definition of 'To improve upon'

From: GCIDE

Improve \Im*prove"\, v. i.
1. To grow better; to advance or make progress in what is desirable; to make or show improvement; as, to improve in health. [1913 Webster]
We take care to improve in our frugality and diligence. --Atterbury. [1913 Webster]
2. To advance or progress in bad qualities; to grow worse. "Domitian improved in cruelty." --Milner. [1913 Webster]
3. To increase; to be enhanced; to rise in value; as, the price of cotton improves. [1913 Webster]
To improve on or To improve upon, to make useful additions or amendments to, or changes in; to bring nearer to perfection; as, to improve on the mode of tillage. [1913 Webster]