[chrisweekly]

"The mathematical statements discussed below are provably independent of ZFC (the canonical axiomatic set theory of contemporary mathematics, consisting of the Zermelo–Fraenkel axioms plus the axiom of choice), assuming that ZFC is consistent. A statement is independent of ZFC (sometimes phrased "undecidable in ZFC") if it can neither be proven nor disproven from the axioms of ZFC."

- TFA

[chrisweekly]

"ZFC" is an esoteric acronym; I posted the quote from the article to help others because the title was entirely opaque to me.