breakthrough

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. An act of overcoming or penetrating an obstacle or restriction.
• n. A military offensive that penetrates an enemy's lines of defense.
• n. A major achievement or success that permits further progress, as in technology.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• adj. Characterized by major progress or overcoming some obstacle.
• n. An advance through and past enemy lines (or vice versa).
• n. Any major progress; such as a great innovation or discovery that overcomes a significant obstacle.
• n. The penetration of the opposition defence

from the GNU version of the Collaborative International Dictionary of English

• n. a productive insight.
• n. a sudden change of situation, such as making an important discovery, that permits further rapid advances toward a goal.
• n. a penetration of an enemy's defense in depth and strength.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. making an important discovery
• n. a productive insight
• n. a penetration of a barrier such as an enemy's defense
• v. break out
• v. penetrate
• v. pass through (a barrier)