unmakable
/ʌnˈmeɪkəbəl/Definitions
1. adjective
Impossible to make or create; incapable of being constructed or manufactured.
“The concept of time travel was considered unmakable by most physicists at the time.”
2. noun
A thing that is impossible to make or create.
“The unmakable nature of a perpetual motion machine is a fundamental principle of thermodynamics.”