The sound you make when you squeal. Is allways spelled "Squee!" with a capital "S" and two "e's and allways with one "!" Can also be used as a substitute for "Weee!" and the like. Online it can be used in place of *squeals*.
A sound that one makes in order to release the immense energy build up when one is excited as to stay earth bound. It happens when there are no other words to express the excitement of a squeal with the attention span of a squirrel!