I define work as anything I do that directly adds value to whoever is paying me for that time - client, employer, myself, etc. That clocks in at 3-12 hours a day, depending on day job work load plus side projects, averaging about 3-4 hours.

However, (and this is a big however), I do lots of things that make me a better worker. That includes socializing (sharing ideas), reading, experimenting in different algos, languages, etc. That doesn't directly add value, but it does in the long run.