𝐅𝐀𝐍𝐅𝐈𝐂 𝐓𝐄𝐑𝐌𝐈𝐍𝐎𝐋𝐆𝐘 [1]

RST

RST = Resolved Sexual Tension 

Refers to the presence of a sexual relationship, the 'inevitable' resolution of pre-existing UST; either implied or described. RST may indicate an Established Relationship, or one that becomes so before the story's end. Originated in The X-Files fandom, but has since been procured by several other fandoms as well.