volcanic rock vs basalt

volcanic rock and basalt both are nouns.

Word	Noun	Adjective	Verb	Adverb
volcanic rock	Yes	No	No	No
basalt	Yes	No	No	No

As nouns, basalt is a hyponym of volcanic rock; that is, basalt is a word with a more specific, narrower meaning than volcanic rock:

volcanic rock: extrusive igneous rock solidified near or on the surface of the Earth
basalt: the commonest type of solidified lava; a dense dark grey fine-grained igneous rock that is composed chiefly of plagioclase feldspar and pyroxene

Other hyponyms of volcanic rock include agglomerate, amygdaloid, dacite, volcanic glass, lava, tufa, tuff.

volcanic rock (noun)	basalt (noun)
extrusive igneous rock solidified near or on the surface of the Earth	the commonest type of solidified lava; a dense dark grey fine-grained igneous rock that is composed chiefly of plagioclase feldspar and pyroxene