noun
1. : wood rat ; especially : a large bushy-tailed rodent ( Neotoma cinerea ) of the Rocky Mountain area having well-developed cheek pouches in which it carries food and the miscellaneous objects it has a tendency to hoard
metal buttons and buckles … stored nearby by the pack rats — J.H.Cook
— called also trade rat
2. : one that resembles a pack rat
was a pack rat and saved everything he got his hands on — Charles Willard