StR - Means Static Reign, or Static_Reign. StR is the l33t 0wn3r of j00 all.
Hey, you got StR'd!
Yo, don't be using StR's name in vain, fucker!
On Snapchat, this could mean "Sent To Recents". It's similar to STA (sent to all).
Sexually Transmitted Religion (STR) is when an individual finds themselves becoming involved with a faith, organized religion, creed, or lifestyle that they otherwise would not have were it not for a relationship. Specifically it refers to someone getting involved with something unhealthy or incompatible with their own personal beliefs for the sake of the relationship.
Jack: Did you hear about my brother?
Jill: Yeah I heard he started going to those weird meetings outside of town.
Jack: Don't worry, it's just an STR.
An acronym that stands for "Spontaneous. Tentacle. Rape." Although obscure it is very aptly used in reference to Japanese prints of doujin and animated hentai.
You think you've seen it all but have you heard of STR? It's a very niche genre.