Gigantic means enormously large, far bigger than normal or expected. A gigantic pumpkin at the county fair might weigh 2,000 pounds, dwarfing all the regular pumpkins around it. A gigantic building towers over its neighbors, making them look small by comparison.

When something is gigantic, it's large enough to seem almost mythical. A blue whale is gigantic, growing up to 100 feet long and weighing as much as 200 tons. The Grand Canyon is gigantic, stretching 277 miles across Arizona.

People also use gigantic for things that aren't physically huge but feel enormous in importance or impact. A gigantic mistake might be one that affects many people or causes serious problems. A gigantic success could be an achievement that exceeds all expectations, like a school fundraiser that raises ten times its goal.

While large, huge, and enormous all describe big things, gigantic suggests something almost unbelievably large. When you call something gigantic, you're emphasizing just how impressively massive it really is.