Not 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.’;
Not likely to be true.
‘It's highly improbable that aliens abducted you.’;
Very difficult to deal with.
‘You never listen to a word I say – you're impossible!’;
Not likely to happen.
‘Due to the loss of power, it is improbable that we will begin on time.’;
‘impossible quantities, or imaginary numbers’;
Not probable; unlikely to be true; not to be expected under the circumstances or in the usual course of events; as, an improbable story or event.
‘He . . . sent to Elutherius, then bishop of Rome, an improbable letter, as some of the contents discover.’;
(obsolete) an impossibility
not likely to be true or to occur or to have occurred;
‘legislation on the question is highly unlikely’; ‘an improbable event’;
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.
‘With men this is impossible; but with God all things are possible.’; ‘Without faith it is impossible to please him.’;
having a probability to low to inspire belief
An impossibility; as, he tried to do the impossible.
‘"Madam," quoth he, "this were an impossible!"’;
too improbable to admit of belief;
‘a tall story’;
something that cannot be done;
‘his assignment verged on the impossible’;
not capable of occurring or being accomplished or dealt with;
‘an impossible dream’; ‘an impossible situation’;
used of persons or their behavior;
‘impossible behavior’; ‘insufferable insolence’;
not able to occur, exist, or be done
‘it was almost impossible to keep up with him’; ‘a seemingly impossible task’;
very difficult to deal with
‘she was in an impossible situation’;
(of a person) very unreasonable
‘what an arrogant impossible fool’;