Nolo's Plain-English Law Dictionary

Lawful Permanent Resident (Lpr)

A non-U.S. citizen who has been given permission to make a permanent home (and work) in the United States. Permanent residents are given "green cards" (not really green) to prove their status. U.S. permanent residents may travel as much as they like, but their place of residence must remain in the United States and they must keep that residence on a permanent basis. Otherwise, they'll be said to have abandoned their U.S. residence, and could lose their right to the green card. A permanent resident who leaves the United States and stays away for more than six months risks having the U.S. immigration officials believe that he or she has abandoned residence.