Synonyms and related words :
Herculean, abstruse, acanthoid, acanthous, acicular, acuate, aculeate, aculeiform, acuminate, acute, arduous, barbed, brutal, complex, cornuted, critical, cusped, cuspidate, delicate, demanding, difficile, difficult, exacting, formidable, hairy, hard, hard-earned, hard-fought, hispid, horned, horny, intricate, jawbreaking, knotted, knotty, laborious, mean, mucronate, needle-pointed, needle-sharp, nettlesome, no picnic, not easy, operose, pointed, prickly, pronged, rigorous, rough, rugged, set with thorns, severe, sharp-pointed, spiculate, spiked, spiky, spined, spinous, steep, strenuous, tapered, tapering, thorny, ticklish, tined, toilsome, toothed, tough, tricky, unbated, uphill, wicked