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