Antisocial

In psychology, the term antisocial refers to a personality disorder in which a person consistently disregards and violates other people's rights, not someone who doesn't like to hang out with other people.

The term antisocial is used as shorthand for Antisocial Personality Disorder (APD). In more extreme cases, the term may be used interchangeably with sociopathy , a condition in which the individual lacks a conscience. People speaking of "psychopaths" are also referring to people with APD. People who have an antisocial personality disorder are not psychotic.

Behaviors diagnostic of APD include persistent and characterological disregard of social norms and lawful behaviors, refusal to take work or financial obligations seriously; lying, conning, and cheating; recklessness, impulsivity, aggressiveness and fighting, and a failure to feel bad about any of it.

So what should we call someone who doens't like to hang out with others?

If a psychological professional wants to say someone avoids spending time (or excessive time) with other people, she'd use a different word. For example, she might say the person is introverted, likes to keep himself, prefers his own company, or is uncomfortable with other people, depending on the circumstances.

A "psychopathic" disorder is defined more broadly in the European Union

In the EU, "psychopathic...means a persistent disorder or disability of mind (whether or not including significant impairment of intelligence) which results in abnormally aggressive or seriously irresponsible conduct on the part of the person concerned." While the aggressiveness and irresponsibility speak to the same antisocial diagnosis, the definition is broad enough that it could also refer to other problems or disorders.