nonmalleable

adjective

non·​mal·​lea·​ble ˌnän-ˈma-lē-ə-bəl 

-ˈmal-yə-bəl,

-ˈma-lə-bəl

: incapable of being shaped or altered : not malleable

nonmalleable cast-iron pipe fittings

… he berates conventional views that animals … have a fixed, nonmalleable nature.

—Robert A. Segal

Word History

First Known Use

1829, in the meaning defined above