Gleeking is a slang term for the projecting of saliva from a gland called a submandibular gland. It is located in the lower palate of your mouth. Quite often this occurs by accident, and humorously, yet understandably, it happens in the dentist chair. The practice of doing it on purpose is appealing to juvenile pranksters and it is usually accomplished by pressing your tongue against the roof of your mouth in a and causing the back side of your tongue to put pressure on the gland. Basically, some people can do it and some can’t, similar to tongue rolling.