Weeeell it can get a little complicated due to the somewhat redundant nature, in my opinion, of the term "Steampunk."
For starters Victorian SciFi covers a large swath of the same themes, other things which include aspects also thrown under the "Steampunk" banner would be the early days of Pulp and also Fantasy worlds that have technology.
I won't go into my personal disagreements with the term, but there are a great many things on these boards which I personally wouldn't be surprised if others called Steampunk, it's just the people who have posted them here see them in terms of Victoran SciFi, "Tech"-Fantasy, Pulp, Early Weird War and so on.
Also always nice to meet another Fergal.