unpossible

From Middle English unpossible, equivalent to un- (“not”) +‎ possible.

• IPA^(key): /ʌnˈpɒsɪbəl/

unpossible (comparative more unpossible, superlative most unpossible)

1. (now rare, nonstandard) Impossible.
   • 1526, William Tyndale, New Testament, British Library 2000, p. 119:

     And this is the. vj. moneth to her, which was called barren, for with god shall nothinge be unpossible.

   • 1621, Democritus Junior [pseudonym; Robert Burton], The Anatomy of Melancholy, Oxford: Printed by Iohn Lichfield and Iames Short, for Henry Cripps, OCLC 216894069; The Anatomy of Melancholy: […], 2nd corrected and augmented edition, Oxford: Printed by John Lichfield and James Short, for Henry Cripps, 1624, OCLC 54573970:

     , New York Review of Books, 2001, p.280:

     ’Tis a hard matter therefore to confine them, being they are so various and many, unpossible to apprehend all.

   • 1624, John Smith, Generall Historie, in Kupperman 1988, p.97:

     In the evening we fired a few rackets, which flying in the ayre so terrified the poore Salvages, they supposed nothing unpossible we attempted […].

   • 1665, Robert Hooke, Micrographia, XXI:

     [S]o prodigiously various are the works of the Creator, and so All-sufficient is he to perform what to man would seem unpossible […].

   • 1994, The Simpsons, "Lisa on Ice":

     Ralph Wiggum: Me fail English? That's unpossible!

   • 2008, David Goldberg, Mimecast, "meeting with HKS":

     I think we can all agree that this is unpossible.

In modern use, the term is usually considered non-standard.