A substance abuse definition is very dependent on who we are talking about and how much we know about drugs and alcohol. Many women in America don’t get “drunk” but they will get “tipsy”. Other people “like to drink” to the tune of a short case a night. As you can see the average persons definition is somewhat subjective.
Here is a good, working substance abuse definition. It comes from about.com.
Substance abuse can simply be defined as a pattern of harmful use of any substance for mood-altering purposes.
Here is a fantastic substance abuse definition from Ohio State University’s Wexner Medical Center.
Substance abuse is used to describe a pattern of substance (drug) use leading to significant problems or distress such as failure to attend work/school, substance use in dangerous situations (driving a car), substance-related legal problems, or continued substance use that interferes with friendships and/or family relationships. Substance abuse, as a disorder, refers to the abuse of illegal substances or the abusive use of legal substances. Alcohol is the most common legal drug of abuse.
Here is what happens when too many professional get involved. It looks like most official organizations have decided to use the Diagnostic and Statistical Manual (DSM) 5.
Official Substance Abuse Definition
Definition Abuse (drug, alcohol, chemical, substance or psychoactive substance)
A group of terms in wide use but of varying meaning. In DSM-IV, ‘psychoactive substance abuse’ is defined as a ‘maladaptive pattern of use indicated by … continued use despite knowledge of having a persistent or recurrent social, occupational, psychological or physical problem that is caused or exacerbated by the use [or by] recurrent use in situations in which it is physically hazardous’. It is a residual category, with dependence taking precendence when applicable. The term ‘abuse’ is sometimes used disapprovingly to refer to any use at all, particularly of illicit drugs. Because of its ambiguity, the term is not used in ICD-10 (except in the case of non-dependence-producing substances); harmful use and hazardous use are the equivalent terms in WHO usage, although they usually relate only to effects on health and not to social consequences. In other contexts, abuse has referred to non-medical or unsanctioned patterns of use, irrespective of consequences. Thus the definition published in 1969 by the WHO Expert Committee on Drug Dependence was ‘persistent or sporadic excessive drug use inconsistent with or unrelated to acceptable medical practice’.
Here is a link to more from the DSM V on the subject. It is even longer than that definition but somewhat easier to read. If your really interested go and see.