gum boot vs rubber boot

gum boot and rubber boot both are nouns.

Word	Noun	Adjective	Verb	Adverb
gum boot	Yes	No	No	No
rubber boot	Yes	No	No	No

As nouns, gum boot and rubber boot are synonyms defined as:

gum boot (noun)	rubber boot (noun)
a high boot made of rubber	a high boot made of rubber