Squee is an orgasmic release-like cry of joy, typically uttered upon seeing pictures of, general news about the pending release of, or receiving a much anticipated toy or item. The number of letter "e"s used can vary, but there should be at least two.
Unknown, but Stormtrooper53 will claim first use at the TFINO. He thinks he subconsciously began using it after reading his dad's copy of a Magnus, Robot Fighter graphic novel. Magnus has the ability to fight robots and destroy them WITH HIS BARE HANDS, typically with a judo chop to the neck. "Squeeeee" is the death cry uttered by a vanquished robot. And since the French call an orgasm le petite mort, "the little death"...oh, you're still reading? Look, I'm really stretching to explain this, alright?