1. (a.) Steep and lofty, in a literal sense; hard to climb.

2. (a.) Attended with great labor, like the ascending of acclivities; difficult; laborious; as, an arduous employment, task, or enterprise.

Herculean abrupt abstruse backbreaking brutal burdensome complex critical crushing delicate demanding difficile difficult effortful energetic exacting exhausting fatiguing forced formidable grueling hairy hard heavy hefty intricate jawbreaking killing knotted knotty labored laborious mean no picnic not easy onerous operose oppressive painful precipitate precipitous punishing rigorous rough rugged set with thorns severe sheer sideling spiny steep stickle strained strenuous taxing thorny ticklish tiring toilsome tough tricksy tricky troublesome trying uphill vigorous wearisome wicked