An intermingling of the words gigantic, and enormous. Ginormous. Would be used to describe something the approximate size of a Brontosaurus or huger. Doesn't necessarily have to be tangible thing.
A slang term combining the words "giant" and "enormous". Despite popular belief, ginormous is NOT A WORD. This term should not be used in daily conversations because WE AREN'T IN THE FIRST GRADE!