breakthrough

from The American Heritage® Dictionary of the English Language, 5th Edition.

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

from the GNU version of the Collaborative International Dictionary of English.

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

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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

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

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