(1) The term Hee Hee is used by Michael Jackson as a way to hit high notes.
(2) It is also used for laughing, giggling, or chuckling
(1) Person 1: "Did you SEE M.J preforming last night?!"
Person 2: "Yeah! I loved how he hit the Hee Hee's!"
(2) Person 3: Wanna hear something funny?
Person 4: what?
Person 3: *Says something funny*
Person 4: hee hee!