impossible impossible /ˌɪmˈpɑːsəbəl/

adjective

1. () Not capable of occurring or being accomplished or dealt with  ( impossible )
   not capable of occurring or being accomplished or dealt with
    An impossible dream
   an impossible dream
    An impossible situation
   an impossible situation
   
2. () Totally unlikely  ( inconceivable , out of the question , unimaginable , impossible )
   totally unlikely
     It seemed impossible to solve the complex puzzle.
   It seemed impossible to solve the complex puzzle.
   
3. (used of persons or their behavior) not acceptable or reasonable  ( impossible , unacceptable )
   (used of persons or their behavior) not acceptable or reasonable
    Impossible behavior
   impossible behavior
   

noun

1. () Something that cannot be done  ( impossible )
   something that cannot be done
    His assignment verged on the impossible
   his assignment verged on the impossible