thor·ough / ˈ[unvoicedth]ərō/ • adj. complete with regard to every detail; not superficial or partial: planners need a thorough understanding of the subject. ∎ performed or written with great care and completeness: officers have made a thorough examination of the wreckage. ∎ taking pains to do something carefully and completely: the Canadian authorities are very thorough. ∎ absolute (used to emphasize the degree of something, typically something unwelcome or unpleasant): the child is being a thorough nuisance.DERIVATIVES: thor·ough·ly adv.thor·ough·ness n.