Frequently confused with the Gonfannon.
The gonfalon's primary characteristic is that it is flown from a horizontal bar, usually supported by a vertical upright. It's most common modern usage is ecclesiastical.
Definition from The Oxford English Dictionary.
Definition according to Norris.
In 1545 Pope Paul III (d. 1549) of the house of Farnese appointed his
illigitimate son Peter Louis Duke of Parma and "Standard bearer of the
Church" (Gonfaloniere della Chiesa). In his coat of arms the badge of the
Gonfaloniere, the papal umbrella, appeared between six fleurs-de-lis of
Parma."
Source: Neubecker