1. A Hebrew word used in the Jewish Scriptures (a.k.a. the Old Testament). The word literally means "nations," and is always used within these scriptures to refer to the nations of the world. Significantly, within the Old Testament, Judah (the Jewish nation) itself is called a "goy."
2. In the Old Testament, the Jews were called to be a nation separate from the other nations, which were all Pagan. And so, colloquially, all non-Jewish nations came to be called "goyim" as in "the nations" from which the God of the Old Testament had called upon the Jews to separate themselves.
3. A word used by some Jews to refer to Gentiles (non-Jews). The word can have derogatory connotations, such as the word "black" when used to refer to a persons of African descent. It can be neutral or negative depending on the context and the intent of the speaker.

Singular = goy