Gladstone bag vs portmanteau

Gladstone bag and portmanteau both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gladstone bag	Yes	No	No	No
portmanteau	Yes	No	No	No

As nouns, Gladstone bag and portmanteau are synonyms defined as:

Gladstone bag and portmanteau: a large travelling bag made of stiff leather

Other synonyms of Gladstone bag include Gladstone.

Gladstone bag (noun)	portmanteau (noun)
a large travelling bag made of stiff leather	a large travelling bag made of stiff leather
	a new word formed by joining two others and combining their meanings