Are you sure that definition 1 is in use?
I can’t say for sure about “juggler” in the English language, but in Dutch, the translation “jongleur” is rarely used for simply someone practicing the activity of juggling.
If a Dutch person were to see someone juggling, he’d likely say: “When I walked through the city center I saw someone juggling on the main square”. Only if that viewer would assume that it is the profession or the identity of the person juggling would he likely call the him/her/it a “jongleur”. This is as much true for self identifying jugglers as it is for muggles, where muggles often don’t even consider calling you a juggler, they might say “goochelaar” (magician) or clown.
Also I realized that one might more easily speak of jugglers when one is talking about a group. A single person who juggles in the park a person who juggles, whereas a group of people juggling in the park is a group of jugglers. At least in my head it feels like that. What do you think?