Adjectives

(a)impracticalnot practical; not workable or not given to practical matters“refloating the ship proved impractical because of the expense”, “he is intelligent but too impractical for commercial work”, “an impractical solution”
(s)airy, impractical, visionary, Laputan, windynot practical or realizable; speculative“airy theories about socioeconomic improvement”, “visionary schemes for getting rich”