Meaning of unknown unknown | Babel Free

Definitions

An uncertainty of unknown magnitude, consequence, structure, and probability characteristics, possibly with completely unsuspected existence; something that we don't know that we don't know.

Examples

“This means there are technical unknowns, unknown unknowns, and technical uncertainties in the contract.”

“Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones.”

“NASA officials often talk about the "unknown unknowns" – the unforeseen problems that catch them by surprise.”

CEFR level