The following is reprinted with permission of the author, who submitted it as a comment in the delightfully irreverent Horse Pucky. Therein, the lovely Pam had referred to the military standard "blivet," which consists of 10 lb of digestive effluent in a 5-lb bag. But wait! There's more!
This is for the engineers in the group.
Aerospace engineers (one of which I once was) recognize a unique commercial mutation of the military specification blivet. As you may not want to know, airplane toilets are "serviced" via an offloading hose attached to a valve on the side of the fuselage. Sadly, this valve inevitably gets - um - clogged. With further inevitability, these valves leak a little.
Leakage speeds up as the altitude increases (there is a formula for this), and the leak continues apace as the airplane cruises at 30,000 feet. It's really cold up there. So the leakage tends to form a frozen - shall we say - globule, which adheres tightly to the side of the aircraft. Our globule grows ever bigger as the flight continues and the back-pressure on the valve continues to increase. Inevitably. There comes a moment when our burgeoning "blivet" - you can see how it might have gotten that name - becomes heavy enough to lose adhesion, and it plummets from the heavens.
No, it does not burn up on re-entry (this is no meteorite). Inevitably, the bright blue blivet - you do remember that airplane toilets flush blue, don't you? - anyway, the bright blue blivet always lands in a farmer's field, usually in Iowa, frightening the cows something terrible.
Upon discovering the source of the cows' discomfiture, the farmer inevitably phones the authorities with tales of imminent extraterrestrial invasion. The authorities, having heard it before, call the local airport to inquire. The resulting report inevitably appears in the weekly report that crosses a certain aerospace engineer's desk. About once a week.
That's a blivet.