impracticable; infeasible; unworkable; impossible to carry out
Describes plans, methods, or ideas that cannot be put into practice due to practical constraints.
The plan was judged impracticable due to insufficient budget.
It's correct in theory, but it's an unworkable idea at present.
Compound of 実行 (じっこう, 'execution') + 不可能 (ふかのう, 'impossible').