Pronunciation: (brāk'thrOO"), [key]
1. a military movement or advance all the way through and beyond an enemy's front-line defense.
2. an act or instance of removing or surpassing an obstruction or restriction; the overcoming of a stalemate: The president reported a breakthrough in the treaty negotiations.
3. any significant or sudden advance, development, achievement, or increase, as in scientific knowledge or diplomacy, that removes a barrier to progress: The jet engine was a major breakthrough in air transport.
constituting a breakthrough: engineered with breakthrough technology; Critics called it a breakthrough film.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.