adj. Impossible to dispute or rebut; irrefutable; conclusive.
n. Something that cannot be answered.
the GNU version of the Collaborative International Dictionary of English
adj. Not answerable; irrefutable; conclusive; decisive.
The Century Dictionary and Cyclopedia
Not to be satisfactorily answered; not susceptible of refutation: as, an unanswerable argument.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. impossible to answer
Word Usage
"Burke, Porson, Dr. Warburton, and Dr. Farmer, pronounced this piece of criticism convincing and unanswerable; but Dr. Johnson and Steevens would not be convinced, and, moreover, have contrived to answer the _unanswerable_."