What does ''armchair philosophy'' mean?

It's actually unrelated to terms like "armchair historian" or "armchair quarterback,"

It refers to any a priori philosophical investigation, the idea being that you can't need to do experiments, or conduct surveys, to know, for instance, what is moral, or if we live in the matrix. These are questions whose answer, if there is one, can be discovered just by thinking about it. They are, so to speak, the sort of question you can investigate from your armchair.

Most (in fact, almost all) academic Philosophy is "armchair philosophy," and the term is usually used in contrast with a new philosophical movement called "X-Phi," or experimental Philosophy, popular at a few philosophy departments in the U.S., like Rutgers and UPitt.

In fact, the official X-Phi emblem is a picture of an armchair in flames.

Armchair philosophy derives it's name from Armchair Quarterback. Like an Armchair Quarterback, an Armchair philosopher is not completely involved, but often comments or criticizes without much real authority in philosophy.

I think it refers to someone who isn't really a professional philosopher making a living as a philosopher but someone who just sits at home philosophizing for free with no stake in the outcome.

See also, "Monday morning philosopher."

I wish I didn't know.

I bought this used La-Z-Boy from a university lecturer in Positivism, and it ... won't ... shut ... up.

I'm thinking of having it restuffed.

Philosophy for those who cannot pull themselves up from the arm chair to go learn regular philosophy.

Expressing opinions without qualification(s)! ;-)

It is similar to Metaphysical Modality and Counterfactual Thinking.

It is the type of philosophising done by people who have never had anything concrete to do with the matter they are discussing
eg the man sits there and says "I think we should not pay for the healthcare of those who will not join a healthcare provider or who will not work." Sounds fine in principle, but he has never visited families without healthcare to see if his premise is true, that they WILL not work and do not WANT to pay for healthcare. He doesn't consider that some people find it hard to find work because of their educational limitations or physical disabilities. And, that, even those who work may be denied healthcare for any number of reasons (they may have pre-existing health conditions).
The real philosopher would go and examine his field of interest, and see what the real situation is.

everyone is an armchair philosopher to some degree. every single person capable of thought and motive lives by a list of philosophies, whether or not their deliniated in writing, whether or not they've been "seriously researched." no one is studied on every aspect of their life, and so they act upon philosophies they use to fill in the gaps. being an armchair philosopher, a bigot, an open minded college graduate--these are all activities based on the same spectrum of thought. it's called humanity.

It's like freestyle philosophy.

Is it possible that "armchair" in this case, could simply be a corruption of the word "amateur"?