ambiguity

Definitions:

Uncertainty as to meaning; doubtfulness; state of doubt.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
Doubtfulness of meaning.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
Uncertainty of signification.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
Doubtfulness or uncertainty, especially of language.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)

Usage examples:

There is no ambiguity nor uncertainty in the language; nor was there any difference in the Convention as to the use of it.
- The Rise and Fall of the Confederate Government, Vol. 1 (of 2) by Jefferson Davis
She had listened for its repetition with an earnestness that brooked not ambiguity
- The White Gauntlet by Mayne Reid
It was not such a shameless affair as he had been led by wanton ambiguity of phrase to believe.
- The Passionate Elopement by Compton Mackenzie