Unobtainable means impossible to get, achieve, or reach. When something is unobtainable, you simply cannot obtain it, no matter how hard you try.

Some things are unobtainable because they don't exist: a perfect score of 150% on a test with no extra credit questions, or a recording of Abraham Lincoln's voice (sound recording hadn't been invented yet). Other things might be unobtainable for you right now, like tickets to a concert that sold out in minutes, or a skill level that requires years of practice you haven't put in yet.

The word often describes goals or objects that seem within reach but actually aren't. A collector might search for years for an unobtainable baseball card that was printed only once and then destroyed. Someone might chase an unobtainable level of perfection, never satisfied no matter how well they perform.

It's worth distinguishing unobtainable from merely difficult. Climbing Mount Everest is extremely difficult but not unobtainable: thousands of people have done it. Flying by flapping your arms, however, is genuinely unobtainable: human bodies simply can't generate enough lift.