being a loner or not being very social isn't the same as anti-social. anti-social is a personality disorder defined by:
The Diagnostic and Statistical Manual of Mental Disorders, a widely used manual for diagnosing mental and behavioral disorders, defines antisocial personality disorder as a pervasive pattern of disregard for and violation of the rights of others occurring since age 15, as indicated by three (or more) of the following:

failure to conform to social norms with respect to lawful behaviors as indicated by repeatedly performing acts that are grounds for arrest
deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure
impulsivity or failure to plan ahead
irritability and aggressiveness, as indicated by repeated physical fights or assaults
reckless disregard for safety of self or others
consistent irresponsibility, as indicated by repeated failure to sustain steady work or honor financial obligations
lack of remorse, as indicated by being indifferent to or rationalizing having hurt, mistreated, or stolen from another
The manual lists the following additional necessary criteria:

The individual is at least age 18 years.
There is evidence of conduct disorder with onset before age 15 years.
The occurrence of antisocial behavior is not exclusively during the course of Schizophrenia or a Manic Episode.

now i'm an introverted personality type, i'm secluded and reserved. does this mean i'm anti-social? not at all.