It's a US Service member or LE officer that has been validated in all essential field/Marksmanship task with a issued weapon system M110 or M24 or M40
Example
Service member graduates Fort Benning sniper course. He is sniper qualified. But a SNIPER goes on preform those skills sets as a part of a platoon.
What is a sniper?
Obama got me back into shooting a while back, having been out of it for over four decades from my Army days, which were limited to BT with the M!6.
Started collecting a few rifles and pistols, beginning with "everything's gonna be 22 so I only need one caliber ammo), then moving to the quintessential deer rifle 270 REM but in a homemade "sniper"variation I bought used, came with a genuine (?) Vietnam US Leatherwood Sniper scope with a built in "computer", never learned to use it, think it was missing a part. But the rifle was basically a Savage with heavy barrel and shoots great.
Collected more rifles and started thinking when I was drinking that I'd become a sniper type shooter....... kept collecting guns, hardly ANY of them good for the purpose.
Finally bought a Savage Axis in 6.5 CM and found out what a bit of longer range accuracy was like. Was so pleased with it that when I read about the RPR in 6.5 in Rifleman Magazine, grabbed one, and FINALLY started working towards "snipering". Improved my reloading skills and equipment (a never ending process, watch a lot of Erik Cortina on YT and buy more gear), and begin taking long range shooting courses and then ELR.
Moved from lesser scopes to a few Vortex and finally to a low-end Nightforce, dream of some top notch glass. I'm 70 and the eyes are getting blurry, so glass is more important than ever. (Had a really sweet Sightron before I bought Vortex, it's about as good.) The Nightforce is best, so far.
Ranges longer than 525 yds are scarce in my neck of the woods, and I haven't really mastered the 525 yet, it involves even more scope work than a top rifle and top ammo.
Learning to use Strelok to determine my scope settings.
Recently took a class on a private island, using my RPR 6.5 to hit out to 1350 and a loaner Cheytac to hit at a mile........
I'll be doing this as long as I am able, hooked good and proper. When the Zombies come down our dirt road, I'll be able to make a lot of them go away or go down........yep, need solid head shots to kill a Zombie, I'm told.
But...........
As to, What is a sniper?
I'll let you know when I get there.
ps: But I thank Obama every day for incentivizing me to get decently ready for Covid and Biden. While everyone's searching ammo, I'm reloading and shooting. Thanks, Hussein!