Here is my own definition for you:
Steampunk is about a fictional age where steam was the main source of
energy and power (i.e.: Trains, Machinery, etc ), and the clothing was
typically composed of victorian age clothes (google it), and accessories
that involved crafted pieces made of gears, brass, gold, etc.
A commonplace accessory that hardly goes overlooked being
(typically brass) goggles that sit atop your head, on your eyes, on top of your hats, etc.
I will add further definitions, with links to the page they were found on for credit.
