It's possible you're thinking of a related concept, such as:
* Triple stress: This could refer to placing strong emphasis on three different words or phrases within a sentence, perhaps for rhetorical effect. However, it's not a formal term.
* Triple underline: In some text editors, you can underline text multiple times. This is mostly used for visual purposes and doesn't have any specific meaning.
* Emphasis on three key points: This could refer to a presentation or document where three main points are highlighted. However, this is not a specific term like "triple emphasis."
If you could provide more context about where you encountered this term, I might be able to help you understand its meaning better.