2.nounAny major progress; such as a great innovation or discovery that overcomes a significant obstacle.
"Albert Einstein is credited with making some of the greatest breakthroughs in modern physics."
3.nounThe penetration of the opposition defence
4.nounThe 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.
5.adjectiveCharacterized by major progress or overcoming some obstacle.