Cumbrous

Adjective

 * 1) Unwieldy because of its weight; cumbersome.
 * 2) * 1946: In the course of thousands of years, this cumbrous system developed into alphabetic writing. — Bertrand Russell, History of Western Philosophy, ch. 1

Thesaurus
Latinate, awkward, bombastic, bulky, burdensome, clogging, clumsy, cramped, cumbersome, elephantine, encumbering, forced, formal, guinde, halting, hampering, heavy, hindering, hulking, hulky, impedimental, impeding, impeditive, incumbent, inkhorn, labored, leaden, lubberly, lumbering, lumpish, lumpy, massive, massy, onerous, oppressive, pompous, ponderous, sesquipedalian, stiff, stilted, superincumbent, turgid, unhandy, unwieldy

Etymology
From cumber + -ous.