Literally: intention – operate / fidelity – solid – harden
Alternately: Strict adherence to one’s principles and beliefs, or even to one’s chosen style in an art. Unwavering, uncompromising loyalty to an ideal.
Notes: Even though the meaning is similar, replacing 志操 with homophone 思想, “thought,” is considered an error. So is pronouncing 堅固 as kenko.
There are several other compounds that end in 堅固, all of roughly the same tenor as this, as well as a variety of synonyms using different terms.