The Oxford Thesaurus An A-Z Dictionary of Synonyms - laborious adj.

1) arduous, burdensome, onerous, strenuous, gruelling, back-breaking, Herculean, exhausting, taxing, tiring, fatiguing, wearying, wearisome, toilsome, difficult, tough, hard, uphill, stiff: Few realize how laborious farm work can be. 2) painstaking, detailed, careful, thorough, diligent, scrupulous, exhaustive, steady, steadfast, relentless, unrelenting, dogged, assiduous, sedulous, persevering, persistent, untiring, tireless, indefatigable, unremitting: After laborious research the virus was finally identified. 3) industrious, hard-working, dogged, determined, unwavering, obstinate, stubborn, unflagging, obdurate: He made a laborious effort to get ahead. 4) laboured, strained, forced, ponderous, overworked: The book contains some of the most laborious prose ever written.