in earnest

1. Sincere; determined; truthful.

   "I wasn't in earnest. I only brought it in joke."

   1841 February–November, Charles Dickens, “Barnaby Rudge. Chapter 29.”, in Master Humphrey’s Clock, volume III, London: Chapman & Hall, […], →OCLC

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   She replied, "When did I ever tell you a lie ? I am in earnest."

   1845, Caroline Kirkland, Western Clearings, Wiley and Putnam, page 104

   Samuel was stern, serious and deeply in earnest. He seldom smiled and never laughed. He was uncompromisingly religious, conscientious and morally unbending.

   1916, Elbert Hubbard, “Samuel Adams”, in Little Journeys Vol. 3: American Statesmen

comparative more in earnest · superlative most in earnest

1. With considerable commitment, determination, or effect; significantly.

   It's snowing in earnest right now.

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   The gentlemen wear swords, and may easily have pistols in their pockets—most likely have, indeed. If they fire at each other without effect, then they’ll draw, and go to work in earnest.

   1841, Charles Dickens, chapter 11, in Barnaby Rudge

   But I see that if I were to live in a wilderness I should again be tempted to become a fisher and hunter in earnest.

   1854, Henry David Thoreau, chapter 11, in Walden

   He spoke in earnest of the importance of achieving academic excellence as well as winning football games.

   1995 December 27, Guerry Clegg, “Mason era ends quickly at Georgia”, in Gainesville Sun, retrieved 20 Aug 2010, page 2C

   The Northern Alliance attacked in earnest on Friday night, and the Afghan Taliban soldiers immediately switched sides, while their commanders jumped into pickup trucks and sped south.

   2001 November 14, Alex Perry, “Eyewitness: The Taliban Undone”, in Time

   The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania. The first barrels of crude fetched $18 (around $450 at today’s prices).

   2013 August 3, “Yesterday’s fuel”, in The Economist, volume 408, number 8847

2. Having a sincere intent. (of a person)

   He was talking in earnest, even though his speech carried an ironic tone.

   1 more example

   "I haven't got it, yet," he told her, while she was behind the screen, above which, as she dressed, there now and then were flutters of swung garments. "But I'll find someone. If you're really in earnest about this-you are, aren't you?"

   1913, Edward Marshall, The Master of the House, G.W. Dillingham Company, page 19