Significant means at least 10%
US Code 95, 10 USC 2505: National technology and industrial base: periodic defense capability assessments, From Title 10-ARMED FORCES, Subtitle A-General Military Law, PART IV-SERVICE, SUPPLY, AND PROCUREMENT, CHAPTER 148-NATIONAL DEFENSE TECHNOLOGY AND INDUSTRIAL BASE, DEFENSE REINVESTMENT, AND DEFENSE CONVERSION, SUBCHAPTER II-POLICIES AND PLANNING, http://uscode.house.gov/view.xhtml?req=code+of+federal+regulations&f=treesort&fq=true&num=316
“(8) The term ‘significant reduction’, with respect to expenditures for a program for a fiscal year, means that the amount provided for that program for that fiscal year in the budget, Acts authorizing appropriations, appropriations Acts, or the future years defense program for that fiscal year is less than the amount provided for that program for the preceding fiscal year in the budget, Acts authorizing appropriations, appropriations Acts, or the future years defense program, respectively, for that preceding fiscal year by at least-¶ “(A) the greater of-¶ “(i) the amount equal to 10 percent of the amount provided for that preceding fiscal year; or¶ “(ii) $5,000,000; or¶ “(B) a lesser amount determined significant by the Secretary of Defense or the National Defense Technology and Industrial Base Council.