n.
Pronunciation: ' br ā k- ˌ thrü
Function: noun
Usage: often attrib
Date: 1918
1 : an offensive thrust that penetrates and carries beyond a defensive line in warfare
2 : an act or instance of breaking through an obstacle <a breakthrough agreement>
3 a : a sudden advance especially in knowledge or technique <a medical breakthrough > b : a person's first notable success <a breakthrough novel>