The "decagon" on Saturn

[Hornbein]

I count eleven sides, though it is somewhat ambiguous.

An eleven sided polygon is a hendecagon. I don't care for a chicken motif. How about a French flavor. That's where double, triple, quadruple and so forth come from. I not-so-humbly suggest onzegon.

 

[Baluncore]

There appear to be 11 sides if you interpolate the radials equally around the polygon.

That polygonal figure is only visible because something about its generation is phase locking the circulation. It probably switches between 10 and 11 cycles, which may explain why part of the circulation is not a clear polygon in that picture.

On Earth, the Himalayas phase lock the Northern subtropical jet stream, while the Andes phase lock the Southern subtropical jet stream. The jet streams on Earth are less organised and often slip or gain a cycle or two. The subtropical also often merges with the polar jet streams, with different harmonics.
https://earth.nullschool.net/#current/wind/isobaric/250hPa/winkel3
https://earth.nullschool.net/#current/wind/isobaric/250hPa/winkel3=-180.15,-89.83,266