Yep.
Yeah, Around the world in 80 Days was loaded with cameos, and they were (mostly) credited.
I looked up the definition, and they never say “always uncredited” the most is- “Often uncredited”.
Certainly can be credited, especially with thorough databases like IMDb. I think the distinguishing feature is how big a role and how much screen time the actor has. Chris Evans’ appearance as Johnny Storm in DP&W for example, was a pleasant surprise, especially if you didn’t know he was in it, but he def played a character with dialogue, even if it was cut short. Not a cameo I would say.
I’d say the best operational definition of “cameo” is a small part where the audience is expected to recognize the actor. The recognition is important: Cate Blanchett in Hot Fuzz isn’t a cameo because she was unrecognizable.
An actual cameo is a small but recognizable portrait, after all.
If the part is uncredited (in the film, not the IMDb, which often credits uncredited actors), it’s a good sign it’s a cameo, but not a necessary one.
Interesting. That would make the Princes William and Harry, or Simon Peggy’s appearances as stormtroopers in Star Wars not-cameos, since they weren’t recognizable. Yet I would consider these to be cameos due to the the brief but famous aspect of their appearances.
Yes, but you couldn’t know who they were just by watching the movie (not counting credits, though cameos tend to be uncredited). You need to go to outside the film to know they were there.
(If an actor is credited for a cameo, it could affect how much money they get for their next film.)
A few years later, It’s a Mad Mad Mad Mad World had a similar wealth of cameos, including Jack Benny and Jerry Lewis. According to Wikipedia, they were uncredited. Other short appearances in the movie did result in credits, including a single shot of the then-Three Stooges.
Both 80 Days and World were made in the ‘we’ve got to fight off the threat of television’ era–giving movie-goers more than they thought they were going to get was a smart strategy.
As for what’s a cameo and what isn’t: I’m comfortable with a loose definition prevailing.
I recently rewatched The Blues Brothers and wonder if Stephen Spielberg’s appearance as the tax office clerk would be considered a cameo or a real small role. The movie came out in 1980, so Spielberg, although not an actor, was well-known for Jaws and Close Encounters of the Third Kind. There’s also a ton of well-known and soon-to-be-better-known people in the movie.
I would say that Steven Spielberg in the Blues Brothers certainly feels to me like a cameo. Same with Frank Oz as the checkout guy at the prison.
The Blues Brothers was directed by John Landis and cameos by directors seems to be a signature of his. I know there were a couple in Trading Places and several in Spies Like us.
The IMDB Trivia page says The Blues Brothers and The Empire Strikes Back came out on the same day, but this appears incorrect (Google tells me they were a month apart). It is still kinda cool that both Princess Leia and Yoda were in it.
“Soiled, your prophylactic is!”
This reminds me. The Duke brothers from Trading Places (Ralph Bellamy and Don Ameche) have a brief cameo in Coming to America as a couple of street bums, to whom Eddie Murphy as Prince Akeem gives some money. “Mortimer! We’re back!”
^^^^This 
I also use the term with regard to doctor visits, while waiting once I’ve been taken back waiting for the doctor to make his/her cameo appearance.
Last week I was thinking of the Coming to America one.
Other examples and my opinion…
Naked Gun 33 1/3. The setting was the Academy Awards. Some actors were presenters and others were in the audience and so forth, To me, the presenters were not a cameo, but if they showed them in the audience they were.
Scrooged. It was a television station. They had “promos” that included Lee Majors and Mary Lou Retton. I consider them cameos.
Sometimes they just flat-out tell you:
A group of “E.T. The Extraterrestrial” aliens appear in the background in Star Wars: Episode I – The Phantom Menace. Would THAT count as a cameo?
And how about the first Teenage Mutant Ninja Turtles movie, where the four actors in the turtle suits all make brief appearances as other characters with their faces visible?
That could be more in the category of actors playing multiple parts in a film.
But Simon Pegg was mostly just providing the voice, and was buried under makeup and prosthetics. I’m not sure that I’d consider that a cameo, just like I wouldn’t consider Daniel Craig’s appearance as a stormtrooper one, either, because there was no way that the audience could be expected to recognize them.
I think that, in order to be a true cameo, there has to be the opportunity to spot the actor. Like, I wouldn’t consider Steven Colbert’s appearance in one of the Hobbit/LotR films (I can’t remember which one), or Rob McElhenney’s (cut for time) appearance in Deadpool and Wolverine a true cameo because you’d have to go out of your way to find them.
But that could just be me.
If that’s a cameo, how about a trick-or-treater costumed as Yoda showing up in E.T., much to the surprise of E.T.