Basically, it's someone who appears in a film but who doesn't have a credit with all the other actors.
Usually they're either extras (non-speaking background people) or cameos (small parts done by named actors usually as a favour for someone).
If you can verify that someone appears in a film, but there's no credit for them, then you can add them as uncredited.
Does that help you?

Edit: forgot to say, very often in older films (before the unions etc.), only the main cast were credited, a lot of the smaller roles weren't credited, so you'll find much more uncredited cast for older films than newer ones.

Quoting northbloke:

Quote:
Basically, it's someone who appears in a film but who doesn't have a credit with all the other actors.
Usually they're either extras (non-speaking background people) or cameos (small parts done by named actors usually as a favour for someone).
If you can verify that someone appears in a film, but there's no credit for them, then you can add them as uncredited.
Does that help you?

Edit: forgot to say, very often in older films (before the unions etc.), only the main cast were credited, a lot of the smaller roles weren't credited, so you'll find much more uncredited cast for older films than newer ones.

OK ... I guess that makes it clear to me. So you would actually have to see someone in the film that you know but they are not credited anywhere at the end (or beginning).

I just wondered because when I was doing a contribution today I had some people listed in there as just FIREMAN and wondered if that might be what it meant.

After reading your explanation, I see that this would NOT apply to that.

Thank you for the help.

Mark
.

I added a couple to a TV Series not long ago.. I seldomly add them but was 2 well known actors and it was extremely easy to document... they were mentioned by the series creator in one of the commentary tracks.