washout vs soil erosion

washout and soil erosion both are nouns.

Word	Noun	Adjective	Verb	Adverb
washout	Yes	No	No	No
soil erosion	Yes	No	No	No

As nouns, soil erosion is a hypernym of washout; that is, soil erosion is a word with a broader meaning than washout:

washout: the erosive process of washing away soil or gravel by water (as from a roadway)
soil erosion: the washing away of soil by the flow of water

washout (noun)	soil erosion (noun)
someone who is unsuccessful	the washing away of soil by the flow of water
the erosive process of washing away soil or gravel by water (as from a roadway)
the channel or break produced by erosion of relatively soft soil by water