indeclinable
adjectiveWithout grammatical inflection.
adjectiveOf or being a word that lacks grammatical inflection though belonging to a form class whose members are usually inflected.
In grammar, not declinable; not varied by declension; showing no variety of form for case, number, or the like.
nounIn grammar, a word that is not declined.
adjectiveNot declinable; not varied by inflective terminations.
adjectivenot
A word that is not grammatically inflected.