Assertable and Impossible

adjective

• Capable of being affirmed or asserted.
  • usage: "a quality affirmable of every member of the family"
  • synonyms: affirmable

noun

• Something that cannot be done.
  • usage: "his assignment verged on the impossible"

adjective

• Not capable of occurring or being accomplished or dealt with.
  • usage: "an impossible dream"; "an impossible situation"
• Totally unlikely.
  • synonyms: inconceivable, out of the question, unimaginable
• Used of persons or their behavior.
  • usage: "impossible behavior"; "insufferable insolence"
  • synonyms: insufferable, unacceptable, unsufferable

• (a.) Not possible; incapable of being done, of existing, etc.; unattainable in the nature of things or by means at command; insuperably difficult under the circumstances; absurd or impracticable; not feasible.
• (n.) An impossibility.