steam iron vs smoothing iron

steam iron and smoothing iron both are nouns.

Word	Noun	Adjective	Verb	Adverb
steam iron	Yes	No	No	No
smoothing iron	Yes	No	No	No

As nouns, smoothing iron is a hypernym of steam iron; that is, smoothing iron is a word with a broader meaning than steam iron:

steam iron: a pressing iron that can emit steam
smoothing iron: home appliance consisting of a flat metal base that is heated and used to smooth cloth

Other hypernyms of steam iron include iron.

steam iron (noun)	smoothing iron (noun)
a pressing iron that can emit steam	home appliance consisting of a flat metal base that is heated and used to smooth cloth