packing plant vs packinghouse

packing plant and packinghouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
packing plant	Yes	No	No	No
packinghouse	Yes	No	No	No

As nouns, packing plant and packinghouse are synonyms defined as:

packing plant and packinghouse: a plant where livestock are slaughtered and processed and packed as meat products

packing plant (noun)	packinghouse (noun)
a plant where livestock are slaughtered and processed and packed as meat products	a plant where livestock are slaughtered and processed and packed as meat products
	a building where foodstuffs are processed and packed