doctrinaire

adj. fanatical, dogmatic; impractical

n. impractical theorist, theorist who does not consider practical matters when applying his theories

Noun
1. a stubborn person of arbitrary or arrogant opinions
(synonym) dogmatist
(hypernym) partisan, zealot, drumbeater
Adjective
1. stubbornly insistent on theory without regard for practicality or suitability
(similar) instructive, informative

adj. doctrinaire, doctrinarian; sententious, pompous

n. doctrinaire, impractical theorist, theorist who does not consider practical matters when applying his theories

adj. doctrinaire, fanatical, dogmatic

(n.)
One who would apply to political or other practical concerns the abstract doctrines or the theories of his own philosophical system; a propounder of a new set of opinions; a dogmatic theorist. Used also adjectively; as, doctrinaire notions.