Definition of "breakthrough"

breakthrough

/ˈbɹeɪk.θɹuː/

adjective
not comparable
1. Characterized by major progress or overcoming some obstacle.
2. (immunology) Involving the contraction of a disease by a person with a decreased susceptibility, such as a person who has been vaccinated to help prevent that disease.
  Quotations
  Breakthrough infections (urine infections that develop in children on antibiotics) can occasionally occur, and if they do, different preventative antibiotics can be given or sometimes surgery to fix the leaky valve can be undertaken.
  a. 2005, “Brochure - Urinary Reflux”, in Renal Resource Centre‎, archived from the original on 2004-04-30
  There is also growing evidence that while Omicron may cause many breakthrough cases among previously infected or previously vaccinated populations, the morbidity and mortality associated with the disease among them will be lower, they added.
  2022 January 15, “In open letter, 30 doctors issue appeal against use of ‘unwarranted medications, diagnostics’”, in The Indian Express‎, WordPress, archived from the original on 2022-01-15
3. (medicine) The emergence or one or more symptoms of a condition despite medication or other medical treatment.
noun
plural breakthroughs
1. (military) An advance through and past enemy lines.
2. Any major progress; such as a great innovation or discovery that overcomes a significant obstacle.
  Quotations
  "Secondly, we have to find more cost-effective ways of electrifying. And we've had a real breakthrough in the last couple of years in terms of bridge clearances and immunisation, meaning we've been able to take hundreds of millions of pounds off the cost of electrification.
  2020 May 20, Andrew Haines talks to Stefanie Foster, “Repurpose rail for the 2020s”, in Rail, page 33
3. (sports) The penetration of the opposition's defence.
  Quotations
  But with the lively Dos Santos pulling the strings behind strikers Pavlyuchenko and Defoe, Spurs controlled the first half without finding the breakthrough their dominance deserved.
  2011 September 29, Jon Smith, “Tottenham 3 - 1 Shamrock Rovers”, in BBC Sport‎
4. (construction) The penetration of a separating wall or the remaining distance to an adjacent hollow (a crosscut in mining) or between two parts of a tunnel build from both ends; knockthrough.