Good idea to start a thread on this, although whether it will end in a settlement...er, I'll take a wait-and-see on that.
*Grab a beer, and Prepare Thyselves for Epic Metreon Post*
I think a good place to start is the term "offensive." That is to say, how does that fit into o-sniping as we define it. In this context, I see it as implying that the person doing it is actually playing offense (as opposed to not doing something with offensive value.)
O-sniping is generally regarded at the moment as sitting on one spot and whanging away at enemies in their base with the LR. This is a cloudy definition, because said whanging, depending on how one approaches it, can actually be offense. Similarly, it can be useless (or at best, a mild diversion.)
For this purpose, I'll stick to the idea that our example sniper is usually sitting in one place. close enough to the enemy base to do damage (usually a tower, hill, or ledge overlooking the base.) My thought on the matter is that new nomenclature should reflect the idea of whether this action is actually being "offensive" (which I am defining here to be useful to a team's offense) or not.
I'm pretty sure we'll agree that hitting a HoF is useful. Especially if they are about to cap. (The idea being that you're making life easier on your team's chasers, either by killing the target they've softened already, softening the target to make it easier to kill, or by buying time by killing a prospective capper.)
Beyond that, I regard shooting departing enemies as useful, simply because they'll be weaker by the time they get to your own base (I generally don't find that people stop to heal or respawn when I do that.) And shooting enemies at their base is acceptable if your team is raiding it (to grab or chase or whatever.)
Which leaves us with the guy (I've been guilty of this on occasion, if only out of sheer boredom or tons of alcohol) who nests and just shoots at the enemies as they spawn or hold vigil, regardless of flag or capper or teammate presence. That's pretty useless. There are some other useless things too. But you're probably running low on beer.
So, that's my opinion on useful and useless. I'm sure that could be argued until the end of time... but for new nomenclature, I like "U-sniping" as a term for useless sniping in general. (Props to whoever came up with that.) Has a nice ring. U-snipers- they just snipe U indiscriminately.
("I smell a PUN!")