[from the English idiom “down a rathole” for a waste of money or time] A technical subject that is known to be able to absorb infinite amounts of discussion time without more than an infinitesimal probability of arrival at a conclusion or consensus. “That's a rathole” (or just “Rathole!”) is considered a pre-emptive bid to change the subject. The difference between ratholes and religious issues is that a holy war cannot be pre-empted in this way. Canonical examples are XML namespaces and open-source licensing.