There is no solid definition... The best way to describe steampunk is using a lot of words.

http://etheremporium.pbwiki.com/What+is+Steampunk

I divide "steampunk" into two basic groups:

- Shiny Brass
and
- Old Metal

The first is what our steampunk clothing items are like (high Victorian lords and ladies type of outfits, shiny metal, romance and adventure).

The second is what I think our steampunk CI is more like (worker-bee Victorian era chaps and chits type of outfits, rusty metal, and working to survive in a distopian universe).