Clinically speaking, what are the characteristics of anti-social personality/disorder?

You are right-- there is definitely a difference between lay use of the term "antisocial" and the psychiatric definition. Psychological illnesses are described in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Antisocial Personality Disorder is defined according to the following criteria:

A. There is a pervasive pattern of disregard for and violation of rights of others occurring since age 15, as indicated by three (or more) of the following:

1. Failure to conform to social norms with respect to lawful behaviors as indicated by repeatedly performing acts that are grounds for arrest.

2. Deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure.

3. Impulsivity or failure to plan ahead.

4. Irritability and aggressiveness, as indicated by repeated physical fights or assaults.

5. Reckless disregard for safety of self or others.

6. Consistent irresponsibility, as indicated by repeated failure to sustain consistent work behavior or honor financial obligations.

7. Lack of remorse, as indicated by being indifferent to or rationalizing having hurt, mistreated, or stolen from another.

-DSM-IV-TR, 2004

The DSM-IV is the "final word" on diagnosis, so unless your brother meets at least 3 of these criteria and is at least 18 years old, he would not be diagnosed as having APD. If he does show the symptoms and meet the age requirement, a professional psychiatric evaluation would be necessary to confirm this diagnosis. You should be aware that APD is relatively rare, with an overall incidence of about 1% in the United States.

Regarding terminology, the APD pattern has also been described as "psychopathy" or "sociopathy", which is where terms like "sociopath" (as discussed in Girl, Interrupted) come from.

The DSM-IV is the primary source for basic information on APD, although you may just want to check it out of the library and take a look at the section on APD rather than buying the book (it's a professional reference, not aimed at the general population, and reads as such). If you're looking for more extensive reading material, there are several well-written books on APD. My personal preference for an introduction to the subject is "Bad Boys, Bad Men: Confronting Antisocial Personality Disorder."

Hope this helps! :)

A sociopath is almost the exact same thing. They are moralistic in a sense but in truth mainly have their own moral standards. To simplify it a bit: anti-social people don't care about anyone else but themselves (with maybe a few exceptions) and do whatever they please. I wouldn't call them mopey, just angry and bitter. Don't tell me I'm wrong because I am pretty much anti-social and fit five of the diagnostic criteria, I think I know me.

An Anti Social usually has a disregard for others rights and is indifferent to others feelings which explains their lack of empathy and emotions. Anti Social people usually are more men then women. There are many sources on the Internet which gives a pretty accurate description. They usually are not a person who conforms to social norms.

No, your therapist is right. For instance Ted Bundy exhibited anti-social personality disorder, yet was able to charm and fool many women into trusting him.

Just google "anti-social personality disorder" and you'll find all the info you need.

And yes, it is a sociopath.