1.AdjectiveNot possible; not able to be done or happen.
"It is difficult, if not impossible, to memorize 20,000 consecutive numbers.; Sarah thinks that nothing is impossible because things can always somehow happen."
2.AdjectiveVery difficult to deal with.
"You never listen to a word I say – you're impossible!; This humidity is impossible."
3.Adjectiveimaginary
"impossible quantities, or imaginary numbers"
4.NounAn impossibility.
5.NounA skateboard trick consisting of a backflip performed in midair.