What is the word for when they play reruns all day of a tvshow?

There isn't a single, specific word for when a TV show plays reruns all day. However, there are a few ways to describe it:

* Marathon: This is a common term, especially when referring to a specific event, like a "Friends marathon."

* Re-run fest: This is a more informal way to describe a day filled with reruns.

* Endless loop: This highlights the repetitive nature of watching the same show over and over.

* Replaying: This is a more general term that can refer to anything being played again, including reruns.

You could also use descriptive phrases like:

* Non-stop reruns

* A day of old episodes

* A marathon of classic episodes

Ultimately, the best word or phrase depends on the context and your desired level of formality.