I consider myself Gen Y and lazy.
My definition of laziness is choosing a lower-effort behaviour over a higher-effort behaviour because the short-term returns are better for choosing lower-effort. This is despite the fact that high effort in my experience correlates very well with higher rewards in the medium to long term.
A person who is lazy chooses the lower-effort approach more often than they perceive that they should. This is subjective for a reason. If a person honestly believes that the low-effort approach gives them the greatest return overall, they are not lazy, but efficient. Why would any person exert more effort than is necessary to achieve a given goal?
For analogy, consider taking out a pile of waste cardboard and putting it in a bin outside. It is not lazy to pile it up until it is about the load one could take in a single trip, and then to take it all at once - it is efficient batching. It is definitely silly to take a pile of cardboard to the bin one item at a time!
Lazy is choosing to let the pile grow until you trip over it, but still put it off because you allow the short-term reward (not having to do anything) to outweigh the more substantial long-term cost (worrying about the pile every time you see it / risk of tripping over it / a much bigger task to be done later).
Unfortunately, by that definition, I am lazy. I often choose behaviours that have a small short-term reward in exchange for a far more substantial long-term cost. Thankfully, and largely due to my involvement (lurking) in the personal finance scene this year, I can exclude finances from my list of 'stuff I am lazy about'. I no longer accrue fees for late returns of library books, or late payments of bills, for example.
I am making progress on choosing not to be lazy about my physical health and fitness. I am exercising regularly. I am making progress on eating healthily and well.
However, there are a lot of tasks I am lazy about. I am currently avoiding doing an assignment due later this week. I am also avoiding practicing the piano, doing writing exercises, and working on a website I own - all things that I know I should be doing, and which when engaged in, I enjoy greatly and experience 'flow'.
Yep. I'm incredibly lazy.