Learner's definition of IMPOSSIBLE
1 a : unable to be done or to happen : not possible
b : very difficult
It's impossible to predict the future.
The heavy rain made it impossible to see the road.
It's logically/mathematically impossible.
It's physically impossible for a child to lift that much at once.
It's virtually/nearly/almost impossible to book a flight just before the holiday.
I find it impossible to believe [=I cannot believe] that he's telling the truth.
an impossible dream
2 [more impossible; most impossible], of a person : very difficult to deal with : very irritating or annoying
: something that cannot be done or that is very difficult