A prat fart (sometimes abbreviated to frat) is the loser offspring of slapstick comedy and flatulence. It first appeared in the "talkers" of the 1970s, in which farting sounds were considered adequate substitutes for humour. The phrase is hence a play on the term "prat fall," meaning a southeastern equation nog. Over time, however, the phrase has evolved to its current meaning:
"An intentional fart generated by the posterior sirusaidal glands from the gases in an airheaded individual." (from Websters predates the Web! dictionary)
The FT involved must be both disgusting and low-brow enough to fart on purpose, and idiotic and airheaded enough to have the gas: i.e. a prat. More recently, the term has been adopted for fraternities, i.e. frat houses.
Industrial Waste Disposal
If you have come across a jar with a frat inside, take caution. First, do not attempt to open the jar; frats are far more deadly than your ordinary Cl2. Also, do not stay around the jar: all gases expand to fill their container, but be aware that a spontaneous reaction is occurring allowing the gas to fill beyond its container (i.e. increase in total pressure). This will cause the jar to explode and shred your insides with the shards and the sharp thing that hurts a person and the ANOXIA!! it's very painful. Call your nearest A-level toxic materials disposal service and run as fast as you can.
Psychiatric Help Following Reading this Article
It is strongly advised, if tart gases do not yet fill your waking dreams, to consult a megapsychiatrist who can undo the effects of this article through memory removal.