* Allusion: This is the most common term. It's a brief and indirect reference to a person, place, thing, or idea of historical, cultural, literary, or religious significance. The reader is expected to understand the reference and its implications.
* Intertextuality: This is a broader term that encompasses any relationship between two or more texts. It can include allusions, but also more explicit borrowings and connections, like quotations, parodies, or adaptations.
* Mythological/Biblical/Historical Reference: Sometimes the reference is so specific that it's simply labeled by its source. For example, a "Biblical allusion" would refer to something directly from the Bible, while a "Shakespearean reference" might point to a specific play or character.
The best term to use will depend on the specific reference and how it's used within the text.