Synonyms and related words :
complex, complicated, crabbed, cramp, difficult, garbled, hard, hard to understand, impracticable, impractical, inoperable, insuperable, insurmountable, intricate, jumbled, knotty, obfuscated, obscure, obscured, overtechnical, perplexed, scrambled, too much for, tough, unachievable, unattainable, uncompassable, undoable, uneffectible, unnegotiable, unperformable, unrealizable, unsurmountable, unworkable,