packinghouse vs packing plant

packinghouse and packing plant both are nouns.

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

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

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

packinghouse (noun)	packing plant (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