What is the definition or description of: illegal drug abuse?

Illegal drug use: Any use of drugs both prohibited by law, eg marijuana or illegally obtained such as opiates. Many meds require prescriptions but only a few are addicting, i would use illegal drug abuse to refer to meds obtained illegally and used to excess against prescribed indications.

Drug Abuse: Agree with prior response. In addition, drug "abuse" has a specific connotation to behavioral health providers. It specifically refers to ongoing maladaptive drug use despite awareness of associated distress and/or life role impairment. The use of legally prohibited and/or illegally obtained substances is suggestive of a current, historical and/or future substance misuse condition.