iceberg vs ice mass

iceberg and ice mass both are nouns.

Word	Noun	Adjective	Verb	Adverb
iceberg	Yes	No	No	No
ice mass	Yes	No	No	No

As nouns, ice mass is a hypernym of iceberg; that is, ice mass is a word with a broader meaning than iceberg:

iceberg: a large mass of ice floating at sea; usually broken off of a polar glacier
ice mass: a large mass of ice

Other hypernyms of iceberg include floater.

iceberg (noun)	ice mass (noun)
lettuce with crisp tightly packed light-green leaves in a firm head	a large mass of ice
a large mass of ice floating at sea; usually broken off of a polar glacier