From thorough +‎ going (adjective).^[1]

• (Received Pronunciation) IPA^(key): /ˈθʌɹəˌɡəʊɪŋ/
• (General American) IPA^(key): /ˈθʌɹəˌɡoʊɪŋ/, /-ɹoʊ/

• Audio (General American):

  (file)

• Hyphenation: tho‧rough‧go‧ing

thoroughgoing (comparative more thoroughgoing, superlative most thoroughgoing)

1. With great attention to detail; complete, thorough.

   Synonyms: see Thesaurus:total

   He did a thoroughgoing job of cleaning up the broken glass.

   • 1871, Walt Whitman, Democratic Vistas‎^[1], New York: J.S. Redfield, page 50:

     It must be reiterated, as, for the purpose of these Memoranda, the deep lesson of History and Time, that all else in the contributions of a nation or age, through its politics, materials, heroic personalities, military eclat, &c., remains crude, and defers, in any close and thorough-going estimate, until vitalized by national, original archetypes in literature.

   • 1927, T. S. Eliot, “The Humanism of Irving Babbitt”, in Selected Essays, New York: Harcourt, Brace & World, published 1964, page 425:

     I am myself a thoroughgoing individualist, writing for those who are, like myself, irrevocably committed to the modern experiment.

   • 1938, Xavier Herbert, chapter XI, in Capricornia‎^[2], New York: D. Appleton-Century, published 1943, page 182:

     Mr. Prayter was a thorough-going cleric in the way of eating. He ate till there was nothing left.

   • 1967, Time, "Marijuana is Still Illegal," 29 December, 1967, [3]

     After six months of preparation, Lawyer Joseph Oteri began in September the most thoroughgoing legal attack on antimarijuana laws ever made.

• thorough-going

• going

• thoroughgoingly

• thoroughgo (obsolete)
• thoroughgoer (rare)