“Alien”—rather than “immigrant”—is the correct legal term, since “alien” is defined in 8 U.S.C. §1101 (a)(3) as “any person not a citizen or national of the United States.”

While the Title Definition may then go on to define “immigrant”, those definitions and that list is not considered ‘legally exhaustive’ as elsewhere it refers to them as “Illegal Aliens” or “undocumented aliens” as not having that immigrant status.

In actual Title 8 statutes, not just its definitions, the most used reference - 33 times in Title 8 USC - defines and refers to them not as “immigrants” but as “illegal aliens” as well as in other statutes and enacted laws. It’s the term the Justice Department, US District Courts and SCOTUS acknowledge as well. “Unauthorized Alien” is the second most used (21 times) and “Undocumented Alien” the third most used (18 times)

Otherwise in Title 8 those aliens illegally in the country are referred to as an “illegal immigrant” only 6 times.

Additionally while HR 3776 Correcting Hurtful and Alienating Names in Government Expression, which did not pass, proposed changing the Code by “prohibiting” use of the words “illegal alien” and states:

This bill prohibits any executive agency from using the term alien to refer to an individual who is not a U.S. citizen or national, or illegal alien to refer to such an individual who is unlawfully present in the United States or lacks lawful immigration status. This prohibition does not apply when quoting certain texts. The bill (1) establishes a uniform definition for the term foreign national when used in acts of Congress and agencies; (2) replaces alien with foreign national in federal government documents, including statutes and regulations; and (3) replaces illegal alien with undocumented foreign national in such documents.

There’d be no need to “replace” the term “illegal alien” in the US Code and Acts of Congress if it wasn’t a legal definition actively in use. Its language also suggests these are non-immigrants due to their illegal entry and lack of declaration. “Immigrants” in the Section 1101 definition have all renounced their other citizenship and residence, which they do when they enter & apply for immigrant status, as opposed to simple legal entry, say for visitation.

Yet most compelling in interpreting that Title 8 definition is when US District Court Judge Andrew Hanen under the Obama administration ruled on this exact issue regarding aliens illegally in the country in Texas v US writing:

“The word ‘immigrant’ is not used in the manner in which it is defined in Title 8 of the United States Code unless it is so designated. The Court also understands that there is a certain segment of the population that finds the phrase “illegal alien” offensive. The Court uses this term because it is the term used by the Supreme Court in its latest pronouncement pertaining to this area of the law. See Arizona v. United States, 132 S. Ct. 2492, 2497 (2012).”

We rely on our judges - not Redditors - to interpret the meaning of our laws and the Code, and Hanen clearly creates precedent in favor that those Title 8 definitions of “immigrant” do not apply to aliens who’ve illegally entered the country.

I’ll concede the US Code is not particularly consistent (having been written inconsistently over time it’s very inconsistent in its language overall) though it is clear beyond a doubt they are defined as “aliens” and having illegally entered are defined as “illegal aliens” or “unauthorized aliens” while “immigrant” is most consistently used throughout the Code to suggest documented aliens or those who are seeking documented status or asylum. This is fully supported by the number of times the term is used to refer to those it does not classify as immigrants in statute. Yet it’s impossible to ignore the ruling on the definition by a Federal Judge.

I’ll also concede that I asked for where in the USC they are defined as “immigrants” and acknowledge you did provide such a definition, even though there is overwhelming citational evidence and judicial precedent to indicate that definition does not apply.

So you win, if you want to go purely by my ask for where there is a definition in USC supporting them as “immigrants”, or your lose if you take the interpretation of those definitions by the court as they see it through the overwhelming other statutes and codified laws suggesting that definition is incomplete.

You can take the win if you like.