adjective. Impossible to attain.

Not to be attained or gained.

adjective. Impossible to attain or reach; inaccessible, unobtainable or unapproachable; unable to accomplish; beyond limit.

noun. Anything that cannot be attained.

adjective. impossible to achieve

"Not one of them stood back and said hang on a minute. many of the ‘targets’ (measures of public satisfaction) were unattainable from the start and as such we cannot sign up for it, thanks but no thanks."

impossible  

attainable  explainable  obtainable  sustainable  trainable  

attainable  impervious  impracticable  impregnable  inaccessible  

beyond one  beyond reach  closed forever to  closed to  impenetrable