An immigrant is "a person who comes to a country to take up permanent residence." (Merriam Webster) According to the Department of Homeland Security, "A Green Card holder (permanent resident) is someone who has been granted authorization to live and work in the United States on a permanent basis. As proof of that status, U.S. Citizenship and Immigration Services (USCIS) grants a person a permanent resident card, commonly called a "Green Card.""
"Undocumented Immigrants" do not have a green card and have not taken steps to obtain status as residents of the United States and therefore they are not immigrants. The term immigrant is used as a way to mock people who enter the United States illegally as nonresidents.
The elusive non-white non-US citizen who is capable of both taking all of the jobs from hard-working Americans who are left unemployed, while also at the same time sitting around doing nothing and collecting welfare and other government benefits, thereby leeching off the American taxpayers.
Bob: "Americans can't catch a break! It's these damn immigrants taking all our jobs!"
Also Bob: "My taxes are too high because so much of it goes to support these lazy immigrants who come here just to get public benefits!"
Bob's friend: "That's so Schrödinger's Immigrant, man, occupying both spaces at the same time."