middle buster vs moldboard plow

middle buster and moldboard plow both are nouns.

Word	Noun	Adjective	Verb	Adverb
middle buster	Yes	No	No	No
moldboard plow	Yes	No	No	No

As nouns, moldboard plow is a hypernym of middle buster; that is, moldboard plow is a word with a broader meaning than middle buster:

middle buster: moldboard plow with a double moldboard designed to move dirt to either side of a central furrow
moldboard plow: plow that has a moldboard

Other hypernyms of middle buster include mouldboard plough.

middle buster (noun)	moldboard plow (noun)
moldboard plow with a double moldboard designed to move dirt to either side of a central furrow	plow that has a moldboard