Swallowtail (flag)
In flag terminology, a swallowtail is either
The name comes from the forked tail that is a common feature of the swallow species of birds.
Nautical signal flag for "A"
Common in Scandinavia, this swallowtail flag contains a vertical section in the centre of the fly.
Presidential standard of Iceland
Also common in the Nordic countries, the swallowtail flag contains a third tail (the "tongue") between the other two tails.
This is the shape of the United States' state flag of Ohio, as well as some burgees, private signals and pennants of the International Code of Signals (ICS) use a triangular swallowtail shape.
Burgee of the Detroit Yacht Club
International signal flag for "group"
A guidon is the general name given to a small swallowtail flag. Guidons are used to represent military units and are displayed on vehicles attached to a particular unit. In some countries (such as the United States), guidons do not necessarily have a swallow tail.
...
Wikipedia