1. Movement of cars, trucks, buses, trains, planes, ships, and pedestrians: That highway has a great deal of traffic at noon.

The manager said that most of the store's traffic was from the entrance to the dress department.

2. The changes of locations of passengers, travelers, voyagers, vacationists, and commuters: Dina was told that the evening flight to New York had a lot of traffic.
3. The system of illegally buying and selling things; such as, drugs, weapons, etc.: The federal authorities are striving to suppress the illegal drug traffic; especially, the traffic that is coming from Mexico.

Henry claims that his family has never had any traffic with criminals.

The bootlegger was arrested for his illegal participation in the traffic of illegal liquor.

To pass goods and commodities from one person to another for an equivalent in goods or money; especially, to buy or to sell goods illegally: The student was trafficking in drugs at the university he was attending and he was convicted of such criminal acts.