(1)As a greeting or as a farewell, to be used in general speak as a substitute for a much better, more difficult salutation.
(2) As a substitute for an affirmative response.
(3) As a substitute for virtually any interjection.
(1)Fred: I'll see you tomorrow, Chuck.
Chuck: OK Fred. Hizzoo!
(2)Fred: Are you going to the movies?
(3) (A) Fred: Jeter just hit a Home
(B) Fred: I won! I won! Hizzoo!
(C) Fred: Didn't that movie rock?