A term used primarily within 12-step programs. The meaning differs by context. The most fundamental of the definitions is a person's belief that he is so unique that the usual rules do not apply to him. Those who use the term believe terminal uniqueness to be a form of pride or egotism. While this sounds at first glance like a person who believes himself to be better than others, it does not have to be.
It is commonly used for the person who believes that nobody in the world has ever had problems as bad, sins as unforgivable, or circumstances as unusually grotesque as his before. "You people couldn't possibly help me, I'm too messed up. You could never understand what I've been through. And I'm an all-around bad person." Through talking to other people who have been through similar things, he usually finds that he shares both shortcomings and circumstances with at least some of them.
It can also be used for the person who wanders into an AA meeting and says, "I'm not like any of you. I never lived on the streets. I never resorted to crime. I was never a crack whore. I never did injectable drugs. I have a job that makes good money." As in the first case, prolonged exposure to others in the group reveals similarities the person was not expecting.
Terminal uniqueness is said to hold a person back from making the progress she needs to make her life better. In an artificially elevated or degraded position, she believes that the advice others give him cannot possibly apply to her. The possibility of her death if she does not improve her life gives rise to the word terminal.
A related usage of the term has been a cause for concern for some people. This is the reference to someone who believes he is so special that, for instance, he can skip some of the 12 steps or arrogantly make up his own way of doing things.
While there are real instances in which people use this mindset to evade responsibility, there is potential for grave misuse of the term. An alcoholic who wants to learn to drink moderately rather than abstain, or an addict who wants to quit using some other method than the 12 steps, might unjustly come under fire as being terminally unique. People can use the concept of terminal uniqueness to browbeat someone into avoiding any semblance of individuality at all.
It may also, especially when applied in a knee-jerk fashion, be used to gloss over the real differences between people. Some autistic people I've known, for instance, have found that within AA or NA their sponsors misjudge their behavior due to neurological differences in body language and social skills. When they try to explain, though, they may be told to give up on their terminal uniqueness and quit expecting special treatment and exemption from the rules. Sometimes a person is just being honest.
Example usage: "When I first started coming here, I had no clue why I was even here. I didn't seem to be as bad off as anyone there. But once I got over my terminal uniqueness, I found out that they had a lot of useful advice."