When you and another person share the side effects of a given drug. I.E. Are you and your friend are both angry drunks? Then you're fx twins!
Jack: bro, everytime I smoke my left arm falls asleep.
John: yo we're fx twins, the same shit happens to me smh!
John: yo we're fx twins, the same shit happens to me smh!
by Tony Left March 3, 2016