RichThesaurus
noncombustible
vs
unflammable
noncombustible
adj
That will not readily ignite and burn.
noun
Any substance that is not combustible.
unflammable
adj
Not flammable.
How often have the words
noncombustible
and
unflammable
occurred in a corpus of books?
(source:
Google Ngram Viewer
)