a person that comes to stay with you for a specified amount of time, from another country, and helps you learn their language. usually.
Dude 1: Man who are those people? I cant understand a word they're saying
Dude 2: You're so dumb, they're obviously exchange students!
A teenager who spends a few months up to a year in a different country experiencing a new culture, living with a new family, and going to a new school. Exchange students will make you question how and why you do things. If you are really lucky, they will bring you candy and other goodies from their home country.
Who is the new girl in chemistry who has an accent?
Oh, she is the new Italian exchange student.