Gigantic means huge — so big that the size is the first thing you notice and the last thing you forget. A gigantic wave, a gigantic queue curling round the building, a gigantic dog that still thinks it is a lap dog.
It sits above big and large, level with enormous and massive, and it works for real size and for exaggeration alike: a gigantic mistake, a gigantic waste of an afternoon. Because it is already at the top, very gigantic sounds wrong to a native ear — absolutely gigantic is how English pushes it further. The giant inside the word is still visible, which is why it suits things with a shape you can picture: a gigantic statue, gigantic ears, a gigantic hole in the road. For amounts and abstractions, enormous and huge do the same job more quietly.
Gigantic comes straight from Ancient Greek γιγαντικός, built on γίγας, 'giant'. The Poly-Olbion project credits the poet Michael Drayton with putting the English word into print in 1612, which makes gigantic younger than most of Shakespeare's plays — though the giant inside it is thousands of years older.
Ancient Greek
γιγαντικός
English, today
gigantic
Built from
From Ancient Greek γιγαντικός, ultimately from γίγας (“giant”). According to the [http://poly-olbion.exeter.ac.uk/the-text/words/gigantic/ Poly-Olbion project] coined by Michael Drayton in 1612.
Etymology from Wiktionary, CC BY-SA