Unfeelingness is a related term of impassiveness.
As nouns the difference between unfeelingness and impassiveness
is that unfeelingness is the state or condition of being unfeeling while impassiveness is the state of being impassive.
unfeelingness
English
Noun
(-)
The state or condition of being unfeeling.
impassiveness
English
Noun
(-)
The state of being impassive.
Synonyms
* impassivity