I certainly agree with hm--us's intention here, and with her general point that "This point has been raised before, but I'm trying again because I think it's important. LEO offers seven similar translations for this phrase, but none at all reflecting this meaning, which is now the only normal one in AE. This gap is very misleading, since the existing translations of 'moot point' in LEO are for all practical purposes incorrect in normal AE usage. "
I will add a few additional thoughts.
While the dictionary definitions given above (#0) are "correct" in proper context, I think they might be less than completely clear or consonant with how the word "moot" is generally used in AE. For example, I do not believe that "moot" and "irrelevant" are always interchangeable.
Black's Law Dictionary gives this definition of moot:
Generally, an action is considered "moot" when it no longer presents a justiciable controversy because issues involved have become academic or dead. Case in which the matter in dispute has already been resolved and hence, one not entitled to judicial intervention unless the issue is a recurring one and likely to be raised again between the parties.
I will add that Black's does (rather strangely, IMO) include this additional definition of "moot":
"A subject for argument; unsettled; undecided. A moot point is one not settled by judicial decisions."
The only time I hear or read the word used that way is in the phrase "moot court," which is something American law students endure as part of their training. In a moot court, the two sides argue the competing points of an issue or set of issues. Except for that limited situation, it would (IMO) be confusing or misleading to use "moot" in a way different from the first Black's definition I quoted above.
(I do not mean to say that the dictionary definitions provided in #0 are not useful or "correct.")