@ichigoteguz
It refers to when another group starts to translate and release a manga when another group is doing so. Such as what’s happening here when we have both Letitgo/CAT scans, and awootism
Awootism here would be considered the sniper as one: godric is a member of the letitgo scam group on here, and two: awootism only has the 4 chapters of mushoku tensei uploaded here and nothing else for the past month.
People tend to snipe whenever a group has issues with staff or translating. Instead of properly contacting the group and saying ‘hey I’ll translate this for you guys!’
It can lead to scanlation groups dropping manga altogether, leaving the sniper to deal with obtaining raws and working on it solo(almost never works out), or ignoring the sniper and waiting them out as previously mentioned, snipers tend to do a small bit, maybe a volumes worth of chapters, then stopping.
Edit: sorry for the overzealous reply, snipers get my blood boiling. I remember drama between an old precursor to mangadex and another... fox based site.