I really hope this isn’t a phenomenon specific to my family otherwise I could risk sounding like a bit of a freak. But what the hell.
I've only ever really discussed this with my brother and he claims to have experienced it too. (I use the word discussed lightly as it was hardly much of a high brow knowledge exchange). But this does happen to me. Not very often granted, but it does happen.
It always takes you by surprise. Your mouth is usually slightly open, and you do something unconsciously with your tongue (I'm not sure exactly what though) and a pretty noticeable amount of saliva spurts from underneath it and out into the world. Unlike most spitting attempts however this spray kinda shotguns out, spraying anything in front of your self in a wide arc. If you are reading it will pretty much cover your page in lots of random daubs of spittle .
The frustrating part for me is that you can never repeat the feat when you try to. It only happens accidentally. God knows my brother and I have tried many times to spray each other in this manner deliberately, facing each other with our mouths open and tongues rolled back, under tongue muscles pumping frantically, mom cheering us on, but to no avail. (Okay so I probably am a freak.)