Definition: A "drug dealer" is a person who sells illegal drugs. These are substances that are not allowed by law to be bought, sold, or used without a prescription.
In more complex discussions, you might encounter the phrase "drug trafficking," which refers to the larger operation of moving illegal drugs from one place to another, often involving multiple drug dealers and organized crime.
While "drug dealer" specifically refers to someone selling illegal drugs, it can also be used in a more general sense to describe someone who sells any type of drug, including legal ones like prescription medications, but usually the term implies illegal activity.
In summary, a "drug dealer" is someone who sells illegal drugs, and this term is associated with crime and legal issues.