topsoil vs dirt

topsoil and dirt both are nouns.

Word	Noun	Adjective	Verb	Adverb
topsoil	Yes	No	No	No
dirt	Yes	Yes	No	No

As nouns, dirt is a hypernym of topsoil; that is, dirt is a word with a broader meaning than topsoil:

topsoil: the layer of soil on the surface
dirt: the part of the earth's surface consisting of humus and disintegrated rock

Other hypernyms of topsoil include soil.

topsoil (noun)	dirt (noun)
the layer of soil on the surface	disgraceful gossip about the private lives of other people
	anything regarded as making something unclean
	the part of the earth's surface consisting of humus and disintegrated rock
	obscene terms for feces

topsoil (adjective)	dirt (adjective)
	(of roads) not leveled or drained; unsuitable for all year travel