1.nounAn illegal immigrant of any country."1990: United States. Congress. Senate. Committee on the Judiciary, Confirmation Hearings on Federal Appointments: Hearings Before the Committee - An agent, Larry Moy, when asked to define the derivation of the term “tonk,” replied: “...it's the sound of flashlight hitting somebody's head, tonk". [This "derivation" is incorrect - see Etymology]"