packrat vs pack rat

packrat and pack rat both are nouns.

Word	Noun	Adjective	Verb	Adverb
packrat	Yes	No	No	No
pack rat	Yes	No	No	No

As nouns, packrat and pack rat are synonyms defined as:

packrat and pack rat: any of several bushy-tailed rodents of the genus Neotoma of western North America; hoards food and other objects

Other synonyms of packrat include bushytail woodrat, Neotoma cinerea, trade rat.

packrat (noun)	pack rat (noun)
any of several bushy-tailed rodents of the genus Neotoma of western North America; hoards food and other objects	any of several bushy-tailed rodents of the genus Neotoma of western North America; hoards food and other objects
a collector of miscellaneous useless objects	someone who collects things that have been discarded by others