Adjective

1. Of or pertaining to a large mass; weighty, heavy, or bulky.

   A massive comet or asteroid appears to have ended the era of the dinosaurs.

2. Much larger than normal.

   Compared to its counterparts from World War II, the Abrams main battle tank is truly massive.

3. Of great significance or import; overwhelming.

   The enlightenment comprises massive shifts in many areas of Western thought.

4. Of particularly exceptional quality or value; awesome.

   Did you see Colbert last night? He was massive!

Synonyms

bulky, heavy, hefty, substantial, weighty colossal, enormous, gargantuan, giant, gigantic, great, huge, titanic consequential, meaningful, overwhelming, significant, weighty awesome, super, excellent, stupendous

Antonyms

insubstantial, light dwarf, little, microscopic, midget, minuscule, pint-sized, tiny, wee inconsequential, insignificant, piddling, trifling, trivial, unimportant lame, stale, disappointing, crappy