topside vs weather deck

topside and weather deck both are nouns.

Word	Noun	Adjective	Verb	Adverb
topside	Yes	No	No	No
weather deck	Yes	No	No	No

As nouns, weather deck is a hypernym of topside; that is, weather deck is a word with a broader meaning than topside:

topside: (usually plural) weather deck; the part of a ship's hull that is above the waterline
weather deck: upper deck having no overhead protection from the weather, but sheltering the deck below

Other hypernyms of topside include shelter deck.

topside (noun)	weather deck (noun)
(usually plural) weather deck; the part of a ship's hull that is above the waterline	upper deck having no overhead protection from the weather, but sheltering the deck below