/he lay"sheuhs/ , adj. Slang.
1. remarkable; astonishing: They're raising a hellacious amount of money in taxes.
2. formidably difficult: We had a hellacious time getting here in the blizzard.
Also, hellaceous .
[ HELL + -acious (extracted from AUDACIOUS, SAGACIOUS, VIVACIOUS, etc.), perh. with intensive or aug. force; cf. BODACIOUS, splendacious ]