Normally, 'squee' is a verb. As in, 'I squee, you squee, he/she squees, they squeed, squeeing, etc.'
However, in continua where 'squee' is already established as a noun, the act of squeeing produces large versions of whatever/whoever the word refers to in the continuum in question. These apparitions are called Piercing Squees.
For example, in the Myst 'verse, a 'squee' is a small furry rodent. In this canon, a Piercing Squee would manifest as a giant one of these squees and then swoop down on whoever did the squeeing to glomp them. They then vanish.