I've thought about this long and hard.... because
I find LR and XLR endlessly fascinating. 
Usually, when something is designated a "long range shot" —
it's because of the difficulty involved when compared to a "normal range shot."
Here's a list of
the type of difficulties
that could be involved.
Often there is a combination of various, and some don't apply to your shooting scenario): ➊ Iron sights, a laser sight, a dot sight, or a scope with only a simple reticle without holdoff subtensions —
all these sights lack holdover aids so that they do not allow you to hold over
with precision to compensate for the projectile's drop. And holdover increases as range increases. Holding 1 inch obove the kill zone* is quite doable, but try 13.75 inches....
*(Though it's easy shooting paper targets, just walk your shots, until you know that your POI is the number 4 on the ring....)
(I understand that a few of the above sights sometimes have basic aiming aids, like pre-set iron sights.)
➋
On far away targets you might have to hold over so much — that your
scope's field of view is too small to allow you to see the target itself, only the point you are holding over on (PasadenaMike's very valid point).
Note that you could combine compensating for the projectile's drop by adjusting both the elevation turret
and using whatever holdover is available in the reticle. (Strelok even has a function for that.)
➌
In windy conditions — for first shot hits* —
wind estimation is critical, and increases in importance and difficulty as range increases.
Depending on the
wind estimation method this difficulty is
medium (with a wind meter like a Kestrel), or
high (when simply guesstimating).
*(not shooting groups)
(This is not a factor if you're shooting indoors — a reason that indoor shots should be longer in order to be considered "long range".)
➍
On far away targets — for first shot hits* —
range estimation is critical, and increases in importance and difficulty as range increases.
Depending on the
range estimation method this difficulty is
low (with a laser range finder), or
medium high (when parallax ranging ranges beyond 40y as is done in field target), or
very high (when simply guesstimating).
*(not shooting groups)
➎
With guns that are notoriously difficult to shoot the definition of "long range" should be at a shorter range. Example: springers in comparison to PCPs.
➏
On far away targets — for first shot hits* —
BC estimation is critical, and as range increases, the importance to know it, and the difficulty to ascertain it also increases.
As range increases, BC increasingly impacts both projectile drop and wind drift, making first shot hits more difficult if one has only an unconfirmed BC number from the internet.
*(not shooting groups)
➐ What can you add to this list?
Matthias
(1) The original post was asking us to define what we consider to be "long range."
