ISO is a standards organization, also the acronym is often used to describe ASA/film speed, but I've not heard someone refer to ISO in a video context, as there is no film.
Are they referring to a specific exposure setting?

Well, I guess you can do it in video just the same, because using an exposure meter the sensitivity of the camera can be determined in equivalent film speed. The Z1 is about ISO 160, at 0dB, 1/50 sec, 25fps.

It's a term that's used a lot in TV sports for playback purposes. As the game (golf, racing, hockey, etc.) is progressing, the director will call for a specific camera to be iso'd. This means that it's feed is recorded separately (usually to a hard drive of some kind) for almost instantaneous) playback.
I've also seen specific cameras being iso'd for an entire game for the same purpose.

Mike

Not just limited to sports, anything that's going through a switcher might also have one or more cameras also feeding decks as well as the switcher. I guess Iso = Isolated.

Bob.

This was in connection with a sports shoot so that must be it - thanks for the replies.

For what it's worth, I used to work as a freelance cameraman for a Miss America state preliminary pageant (I'd better not name the state). One year in particular, on Saturday afternoon (technical rehearsal day), I remember well one of the engineers working in the truck would ISO my camera feed and my clear-com channel (on the headsets) and ask me to zoom into a few of the lovely ladies on stage, and throw my lens extender on! There'd be a period of silence on the headsets for a few minutes, then I'd hear him say, it was OK to zoom back out.

I can only imagine the dirty tricks going on in the truck when things were getting really boring!

I do corporate video projects and occasionally we'll have an event that we'll use several cameras on. For instance, a training film of role-play between a sales rep and a customer. We'll use one camera from the customer's point of view, one from the rep's and the third to include both rep and customer in the shot. We'll roll tape in all three cameras, but (as was mentioned in an earlier reply) we'll also have a 4th tape rolling that records a switched feed from any of the three cameras we choose. Essentially, we're editing on the fly with the switching technician literally "calling the shots" (usually through a clear-com head set tothe rest of the camera crew). Depending on the abilities of the technician doing the switching, this "ISO" (isolated) reel could be very close to the finished product. I'll usually capture that tape to Vegas and fine-tune the editing. Sometimes the technician will make an error in their switching decision, in which case I'll go to the individual camera tapes to get the shot they missed.
For what its worth, ISO would be a better name for the individual camera tapes, since they're isolated and MIX would be a better name for the switched recording (but tradition is hard to buck)..