What do you call a person who speaks 3 languages?

My Spanish-speaking students got a kick out of this one.

Q: What do you call a person who speaks 3 languages?
A: (Try to elicit responses..) Tri-Lingual.
Q: What do you call a person who speaks two languages?
A: (Many of them know this one) Bi-Lingual.
Q: What do you call a person who speaks one language?
A: An American!