rolling jam

At a session/open stage:

Someone starts, without stopping, other enter, some leave.

No discussions, everyone can enter, everyone should leave after some time.
On entrance one nicht bring up a thing/theme.

Variation 1: kicking jam, every enter is accompanied by a leave. Means the number of people on stage has a limit.

Variation 2: put a limit on peoples stage time, e.g. a change after 3 minutes.

rehearse !

I participate in rehearsels, regulary, weekly, but I do not organize one myself.

I call it expanding and practicing my repertoire  of answers, questions and reactions for musical environments.

This seams to fit most activities to me, when they are done proper.