im·pos·si·ble /imˈpäsəb(ə)l/ Learn to pronounce adjective not able to occur, exist, or be done. "a seemingly impossible task" Similar: not possible out of the question not worth considering unfeasible impractical impracticable nonviable unworkable beyond one unthinkable unimaginable inconceivable paradoxical illogical irrational undoable like herding cats unattainable unachievable unobtainable hopeless implausible far-fetched forlorn vain incredible unbelievable absurd ludicrous ridiculous laughable risible preposterous outlandish outrageous wild harebrained Opposite: possible easy attainable very difficult to deal with. "she was in an impossible situation" Similar: unbearable intolerable unendurable unsustainable no-win Opposite: bearable tolerable INFORMAL (of a person) very unreasonable. "what an arrogant impossible fool" Similar: unmanageable intractable recalcitrant wayward objectionable