unobtainable adjective 1noun 1forms 3 adjective1 •Unable to be obtained: not able to be acquired or reached.With secondhand bullhead rail almost unobtainable, the NYMR has been forced to go for new flat-bottom rail and orders are being placed; 58 fb rails are already en route to the railway. — 1979 noun1 •Someone or something that cannot be obtained.On the whole they are at present fairly cheap, and are not overburdened with long priced stamps, and still fewer unobtainables. — 1896 formsunobtainables · more unobtainable · most unobtainable