1.  pack rat(n = noun.person) magpie, scavenger - someone who collects things that have been discarded by others;
is a kind of hoarder

2.  pack rat(n = noun.animal) bushytail woodrat, neotoma cinerea, packrat, trade rat - any of several bushy-tailed rodents of the genus Neotoma of western North America; hoards food and other objects;
is a kind of wood-rat, wood rat
is a member of genus neotoma, neotoma
has particulars: dusky-footed woodrat, neotoma fuscipes

1.  Any of several bushy-tailed rodents of the genus Neotoma of western North America, especially Neotoma cinerea, which hoard food and other objects in their nests. [WordNet 1.5]

2.  A person who habitually saves items, even those unlikely to be useful. [PJC]

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