"rearcock" is a slang term used in the context of adult content, and it's understood to mean a certain kind of sexual act. It is derived from the English words 'rear' (meaning backside or buttocks) and 'cock' (a slang term for penis).
In adult video tags, "rearcock" refers to scenes where a man performs oral sex on another man by stimulating his erect penis with his mouth or tongue while his partner is bent over in such a way that the performer can access his genitals from behind. It's often associated with bareback or unprotected anal intercourse, which adds an element of risk to the scene due to the potential for STIs.
Note: This tag may not be universally understood and might differ based on regional slang and cultural differences. It is specifically intended for adult audiences familiar with adult content terminology.