A spin on "OPSEC", short for "operational security". OPSEX is keeping the relationship your parents don't approve of under wraps. It's keeping that side piece on the down low.
In the current year, opsec is being used by an increasing number of everyday people to mask or spoof their online identities which are being aggressively tracked and recorded by governments and big tech.
Coming from the word obsess, obsex is when someone is fully consumed with the thought of having sex with a particular person. Obsessed with sex is obsexed.
Yo man! Damn, I couldn't sleep at all I was so obsexed with the chick I saw at the partylast night.