Pronunciation: (mas'iv),[key] —adj. 1. consisting of or forming a large mass; bulky and heavy: massive columns. 2. large and heavy-looking: a massive forehead. 3. large in scale, amount, or degree: a massive breakdown in communications; massive reductions in spending. 4. solid or substantial; great or imposing: massive erudition. 5. Mineral.having no outward crystal form, although sometimes crystalline in internal structure.