impracticable

adj

1. Not practicable; impossible or difficult in practice.

   “It has not been used for many years, and although it was impracticable to photograph the engine in the small confines of the shed it was possible to obtain a picture of the plate which it still carries showing the former ownership.”

   “Prison abolitionists are dismissed as utopians and idealists whose ideas are at best unrealistic and impracticable, and, at worst, mystifying and foolish. This is a measure of how difficult it is to envision a social order that does not rely on the threat of sequestering people in dreadful places designed to separate them from their communities and families.”

2. impassable (of a passage or road)
3. (obsolete)unmanageable

   “And yet this tough impracticable heart / Is govern'd by a dainty-finger'd girl ; […]”

   “H. is a person of extraordinary health & vigor, of unerring perception, & equal expression; and yet he is impracticable, and does not flow through his pen or (in any of our legitimate aqueducts) through his tongue.”

noun

1. (obsolete)an unmanageable person

   “They were not allowed, of course, to join us in the sitting room, partly that their practice might not be disturbed, but principally, that I was looked upon as an utter impracticable.”

   “The strict constructionists had dwindled to a few impracticables, headed by John Randolph.”

   “Then there are the gladiators, to whom it is always a battle; 't is no matter on which side, they fight for victory; then the heady men, the egotists, the monotones, the steriles, and the impracticables.”