Anti-social behaviour (with or without hyphen) is behaviour that lacks consideration for others and that may cause damage to society, whether intentionally or through negligence, as opposed to pro-social behaviour, behaviour that helps or benefits society (Berger 2003, p. 302).

In common parlance antisocial is often used to describe those perceived to be excessively introverted, an incorrect though increasingly common usage.

or

Antisocial Personality Disorder (ASPD or APD) is defined by the American Psychiatric Association's Diagnostic and Statistical Manual as "...a pervasive pattern of disregard for, and violation of, the rights of others that begins in childhood or early adolescence and continues into adulthood

(both wikipedia entries)