Definition: extremely large

Ginormous, a portmanteau of gigantic and enormous, traces back to World War II and was first recorded in a 1948 British dictionary of military slang (though recent research has found the word used in British newspapers as early as 1942). Examples of its use found in a 1962 dictionary of sailors' slang include "a ginormous brush with the enemy," "a ginormous raid," and "a ginormous party in the mess." Now demobilized, ginormousis used to describe anything humongous. 

"The park is so ginormous—840 acres, about 10 times the size of Disneyland—… that families could take several trips and still not see it all." 
—Cindy Carcamo, The Los Angeles Times, 17 July 2016

More at https://www.merriam-webster.com/words-at-play/civilianized-military-jargon?utm_campaign=wap&utm_medium=social&utm_source=facebook&utm_content=military_origins