I thought this definition rocked!
Borderline Personality Disorder is a pattern of instability in interpersonal relationships, self-image, and affects, and marked impulsivity.
Individuals with Borderline Personality Disorder may have a pattern of undermining themselves at the moment a goal is about to be realized (e.g., dropping out of school just before graduation; regressing severely after a discussion of how well therapy is going; destroying a good relationship just when it is clear that the relationship could last). Some individuals develop psychotic-like symptoms (e.g., hallucinations, body-image distortions, ideas of reference, and hypnagogic phenomena) during times of stress. Individuals with this disorder may feel more secure with transitional objects (i.e., a pet or inanimate possession) than in interpersonal relationships. Premature death from suicide may occur in individuals with this disorder, especially in those with co-occurring Mood Disorders or Substance-Related Disorders. Physical handicaps may result from self-inflicted abuse behaviors or failed suicide attempts. Recurrent job losses, interrupted education, and broken marriages are common. Physical and sexual abuse, neglect, hostile conflict, and early parental loss or separation are more common in the childhood histories of those with Borderline Personality Disorder. Common co- occurring Axis I disorders include Mood Disorders, Substance-Related Disorders, Eating Disorders (notably Bulimia), Posttraumatic Stress Disorder, and Attention- Deficit/Hyperactivity Disorder. Borderline Personality Disorder also frequently co- occurs with the other Personality Disorders.
http://www.psych-net.com/disorders.html