glacial boulder vs bowlder

glacial boulder and bowlder both are nouns.

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

As nouns, bowlder is a hypernym of glacial boulder; that is, bowlder 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
bowlder: a large smooth mass of rock detached from its place of origin

Other hypernyms of glacial boulder include boulder.

glacial boulder (noun)	bowlder (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