No, i am not saying that it is undefineable. I am saying that it is definable by the synthesis of the activity and the context that surrounds it, and not by the nature of the activity itself. This goes for all the activities in the genre of juggling, apart from the default form, which is defined by (still working on exact wording):
In terms of the activities in the genre of juggling, I think it could be useful to list what they most commonly consist of. Throwing, catching, twirling, trapping, stalling, balancing etc, as long as we remember that these are not defining properties. You can go as far in depth on those as you would like, I encourage any effort in doing so.
I do not think this is an example of a truth to what juggling is. All I see is one person seeing some connection to what is happening, to what he is already familiar as juggling. I am sure many, or even most people would not make such a connection, and that to them, it is just a guy messing around, trying to trick the spectator to where the ice cream is.
In terms of a connection to the default form, I do not think it has to be a very direct one. As long as there is a connection to something in the pool of activities that are already accepted as juggling, you will have people (such as in the ice cream case) that will make some connection, when they try to categorize an activity. The genre of juggling is already quite extensive, so it does not surprise me that somethings are far from the default form.
I have stated plenty of arguments to why 3b/N+1 is the default form, and I am happy to recap.
The reason why it is the default form is because it is the only activity that is always referred to as juggling, no matter of context.
If you take some other kind of manipulation, such as the kind you find in Rhytmic Gymnastics, jugglers can easily refer to it as juggling, but to most, the word(s) representing that activity is Rhytmic Gymnastics, not the word juggling.
Same goes for cardistry.
Those are examples of argument that show that properties found in juggling outside of the default form, are not defining properties of juggling.
When the word juggling is used, and no further information is given, the default form is generally implied.
When asked “can you juggle?”, the default form is generally implied.
If another default form existed, that should be fairly easy to show. Just give an example of an activity and list the properties it consists of. If it is a default form, every activity where those properties will be found will be referred to as juggling.
“Controlling an object using a stick” is an example of a property that is not a defining one. It is a property that in certain contexts will result in an activity in the genre of juggling. An example is Devil stick. Examples of when it is not juggling are stirring soup, playing baseball, fishing and ice hockey.