glacial boulder vs boulder

glacial boulder and boulder both are nouns.

Word	Noun	Adjective	Verb	Adverb
glacial boulder	Yes	No	No	No
boulder	Yes	No	No	No

As nouns, boulder is a hypernym of glacial boulder; that is, boulder is a word with a broader meaning than glacial boulder:

glacial boulder: a boulder that has been carried by a glacier to a place far distant from its place of origin
boulder: a large smooth mass of rock detached from its place of origin

Other hypernyms of glacial boulder include bowlder.

glacial boulder (noun)	boulder (noun)
a boulder that has been carried by a glacier to a place far distant from its place of origin	a large smooth mass of rock detached from its place of origin