It's used in one idiomatic expression, "the point is moot", which is almost always misused to mean 'irrelevant' rather than 'debatable'. The funny thing about idioms is that many are atomic: native speakers don't bother to dissect the individual words, they use the whole phrase because it signals something specific to other fluent speakers. When you learn a second language (French, in my case), these expressions are interesting because they usually do have an outmoded meaning, but if you ask someone they have a very hard time translating or explaining. They're also a giant pain unless you learn through immersion, because they're habitual and not usually systematic in any way.

The "archaic" usage at that link is actually very much alive, it's a technical term used in law school for mock trials [1]. I would argue law students actually understand the meaning of the term better than average, native English speakers, making the technical term less archaic.

1. http://en.wikipedia.org/wiki/Moot_court