Moot = debatable. so a "moot point" is a topic that is pointless to argue about because it can be debated about for a long time with no resolution or it is not applicable to the topic. In other words; there's no use arguing it. "we should not argue about politics, it's a moot point." or "Discussing the building plans is important, we don't have time to discuss the parking spaces now because it's a moot point (compared to the bigger picture)."

A moot point is a question that is subject to debate or dispute e.g. 'whether the temperature rise was mainly due to the greenhouse effect was a moot point' Can also mean an irrelevant question or point e.g. 'whether or not the chicken came before is a moot point'