Well, if you do a quick google search you'll see :)
“Engine 2 is the full set of adjacent businesses that the company might pursue to replace the declining growth rates of Engine 1. This includes not just growing markets in new geographies, but also new products and services in both existing and new markets.”
So, in essence, it means that our currnet business isn't growing enough to meet our needs. We need to expand elsewhere (into new markets with our existing product, new products in our existing market, or both (risky))