This is Yiddish for a non-Jew. The plural is “goyim.”
It’s disputed as to whether the word is a Semitic slur – a word that Jewish people use to pejoratively refer to non-Jews. Wikipedia has a list of Yiddish phrases where “goy” is meant to refer to something trivial, frustrating, or pointless.
The term is sometimes turned around and used anti-Semitically. For example, a racist might proudly and specifically refer to themselves as a “goy.”
Why I Looked It Up
On an episode of Happy Endings, Penny was wondering why young Jewish boys would always hit on her at Bar Mitzvahs. Jane offered this:
You’re a goy with vaguely Semitic looks.
The implication was that she’s not Jewish but looks like it.