Metro's branding was a failure of imagination and a failure to properly capture and convey intent. There are many other options out there:

| "Touch UI" | "Mobile UI" | "Everywhere UI" | "Fisher-Price UI" |

... or my personal favorite...

| "Mega-Bloks" |

As usual, common sense applies. The issue is regarding unnecessary names. If it's really a product name or industry wide then use it, but many companies tend to come up with acronyms that are only used internally or within a single team and this hurts communication.

For your example, just call it touchscreen mode.

I think pretty much every industry and field quickly develops it's own stock of acronyms, nicknames, jargon etc. This can feel alienating to "outsiders", which is why people don't like it, but I think its pretty necessary (and inevitable). If you're working with a set of concepts, processes, software everyday, developing a shorthand way of talking (and thinking) about them is a big timesaver both in terms of communication and mental effort.

> If you're working with a set of concepts, processes, software everyday, developing a shorthand way of talking (and thinking) about them is a big timesaver both in terms of communication and mental effort.

For internal processes, this is fair enough. But anything that will be exposed to an end-user should be simple without shorthand.

how many new UIs was the windows team developing at the time? shouldn't "the new UI" suffice?

“New” is a bad way to refer to something. It loses meaning once the new thing isn’t so new or has been replaced by something newer.

Say a document talks about “the new windows UI” and there were like 5 different versions of “new ui” during the lifetime of the project. Which version is the document talking about?

Maybe just try really hard to maintain a centralized glossary, that people actually use and keep up to date.

I'd call it the Touch UI, the others could be Windowed and Mobile.