- 1 done completely; with great attention to detail a thorough knowledge of the subject The police carried out a thorough investigation. You will need a thorough understanding of the subject.
- 2 [not usually before noun] (of a person) doing things very carefully and with great attention to detail She's very thorough and conscientious. He was determined to be thorough in his research.
- 3(British English, informal) used to emphasize how bad or annoying somebody/something is synonym complete Everything was in a thorough mess. Word OriginOld English thuruh, alteration of thurh ‘through’. Original use was as an adverb and preposition, in senses of through. The adjective dates from the late 15th cent., when it also had the sense ‘that goes or extends through something’, surviving in thoroughfare.
Check pronunciation: thorough
