Here are some words that get close, depending on the specific aspect you want to emphasize:
* Formatting:
* Plain text: This highlights the simplicity of Markdown.
* Lightweight markup: Emphasizes the minimal syntax.
* Markup language: More generic, but accurate.
* Process:
* Conversion: Focuses on the transformation from Markdown to HTML or other formats.
* Rendering: Describes the process of displaying the Markdown content.
* Styling: Highlights the ability to apply visual styles to the content.
Ultimately, the best word depends on the context. If you're talking about the syntax itself, "formatting" might be appropriate. If you're discussing the process of using Markdown, "conversion" or "rendering" could work.