Pronunciation: (lu-bôr'ē-us, -bōr'-),[key] —adj. 1. requiring much work, exertion, or perseverance: a laborious undertaking. 2. characterized by or requiring extreme care and much attention to detail: laborious research. 3. characterized by or exhibiting excessive effort, dullness, and lack of spontaneity; labored: a strained, laborious plot. 4. given to or diligent in work: a careful, laborious craftsman.