obtundent
Noun
Meaning
A substance which sheathes a part, or blunts irritation, usually some bland, oily, or mucilaginous matter; -- nearly the same as demulcent.
Source: Webster's dictionarySynonyms
hard
hardened
indifferent
insensitive
callous
numb
insensible
unfeeling
unresponsive
imperceptive
impercipient
inured