thorough

American  

[thur-oh, thuhr-oh] / ˈθɜr oʊ, ˈθʌr oʊ /

adjective

1. executed without negligence or omissions.

   a thorough search.

   Synonyms:

   total, unqualified, sheer, downright, exhaustive, in-depth

   Antonyms:

   superficial, partial

2. complete; perfect; utter.

   thorough enjoyment.

3. extremely attentive to accuracy and detail; painstaking: a thorough analysis.

   a thorough worker;

   a thorough analysis.

4. having full command or mastery of an art, talent, etc..

   a thorough actress.

5. extending or passing through.

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adverb

1. Archaic. through.

noun

1. (initial capital letter) the administrative policies of the Earl of Stafford and Archbishop Laud during the reign of Charles I: so called because they were uncompromisingly carried out.

thorough ¹ British  

/ ˈθʌrə /

adjective

1. carried out completely and carefully

   a thorough search

2. (prenominal) utter

   a thorough bore

3. painstakingly careful

   my work is thorough

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Thorough ² British  

/ ˈθʌrə /

noun

1. thoroughgoing policy, as adopted in England by Strafford and Laud during the reign of Charles I

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Other Word Forms

• quasi-thorough adjective
• quasi-thoroughly adverb
• superthorough adjective
• superthoroughly adverb
• thoroughly adverb
• thoroughness noun
• unthorough adjective
• unthoroughly adverb

Etymology

Origin of thorough

First recorded before 900; Middle English (preposition and adverb); Old English thuruh, variant of thurh through

Explanation

Thorough describes something that is painstakingly complete, like a thorough search for your missing keys in which you look for them in coat pockets, under the table, in the refrigerator — in every single place you can think of. Thorough rhymes with "burrow": "THUR-oh." It looks a lot like through but remember thorough is an adjective, so you might use it to describe a thorough investigation or a thorough review. In contrast through is used most often as a preposition — you might look through every drawer, for example, in a search — or as an adverb — you might see a hole in your pocket where coins fall through.

Example Sentences

"We have evacuated the school and will carry out a thorough investigation into this tragic incident," he added.

From Barron's • Apr. 14, 2026

If the allegations are false, he needs to refute each and every detail in thorough, incontrovertible fashion.

From Los Angeles Times • Apr. 10, 2026

"A thorough noise analysis is necessary to assess practical feasibility, but our first estimates are promising."

From Science Daily • Apr. 10, 2026

These are not novels that pull you forward so much as hold you in place—patient, thorough evocations of a vanished world, almost Proustian at times, especially as they progress.

From The Wall Street Journal • Apr. 3, 2026

After your fingerprints are submitted, the FBI conducts a thorough background check.

From "Americanized" by Sara Saedi

Related Words

• accurate
• careful
• complete
• comprehensive
• detailed
• exhaustive
• full
• intensive
• meticulous
• painstaking
• profound