Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

571. Obscurity — N. obscurity &c (unintelligibility) 519; involution;

hard words; ambiguity &c 520; unintelligibleness; vagueness &c 475, inexactness &c 495; what d'ye call 'em &c (neologism) 563 [Obs.]; darkness of meaning. Adj. obscure &c n.; crabbed, involved, confused.