A person, new to The Wild West, who's seen as an acceptable target by the locals. By stereotype, this trope is flashily dressed in big-city fashions, thinks rural folks are idiots, and is unused to manual labor.
The name comes from "slicker" being slang for a newborn calf, indicating how naive the newcomer is about the ways of the West. Yep, it's a subtrope of Naïve Newcomer, and has a strong overlap with City Mouse.
If the city slicker is well-meaning, after a couple of pranks and some honest labor they'll toughen up and learn the new rules. But if they're dishonest folks trying to bilk the locals of their hard-earned cash or land, all bets are off as to their final fate. Note that some confident tricksters will pretend to be city slickers to make themselves seem easy targets.
One act of adolescent rebellion sometimes seen in Westerns is "dressing like a city slicker."
Actually, the Old West had many terms for newcomers, and we'll list a few and their distinguishing features here until they merit their own pages.
Dude: A tourist. (As used in the term "dude ranch".) Just here to soak up some Western flavor and see the sights. Plans to be going back East in a few weeks. Generally not malevolent, but can be pushy and inadvertently offensive.
Greenhorn: Less emphasis on the flashiness and snobbery, more emphasis on the naivete. The Greenhorn wants to do the right thing, but doesn't know the ropes yet. Usually grows into a hardened veteran of the West.
Tenderfoot: The emphasis here is on the soft skin and weak muscles that city life cause. Expect this character to get blisters and be exhausted after even the least demanding chore. Like the Greenhorn, he'll soon toughen up and learn the value of hard work.
Tinhorn: Almost always paired with the word "gambler." The Tinhorn plays down the naivete, and emphasizes the flash and surface wealth. Generally a malevolent figure, though easily vanquished.
- The animated short Wild Life (nominated for an Oscar in 2012) tells the story of a Remittance Man from England who moves to Alberta, and soon finds himself ill-prepared for the harshness of the terrain or the prejudices that the locals have towards the upper-class twits who have descended upon their country. It doesn't end well for him...
- The City Slickers movie invokes this trope with the big city folk learning the value of hard work on a Cattle Drive.
- Here's one for a non-Western setting: In Jaws, Quint is really apprehensive about going out to sea with Hooper and Brody for similar reasons. Hooper is a rich guy (Quint derides his "soft hands... been countin' money all your life."), and Brody is severely afraid of water, though in his case it might be less of a "city slicker" type deal than the fact that he's just The Landlubber.
- Also, Pauly Shore in Son in Law. (Which was, against all expectation, a pretty good movie.)
- Another non-western example: the titular character in the film Jean de Florette fits the "Greenhorn" trope to a T. However, he never becomes a hardened veteran of the west.
- Jimmy Stewart's character in The Man Who Shot Liberty Valance is a Tenderfoot. In a reversal of the usual pattern, he doesn't toughen up to fit the Town, instead acting as a civilising influence. Once, that is, a certain Liberty Valance has been shot.
- In Revenge of the Virgins, Melvin Potter is a tenderfoot from back east who arrives on the frontier looking to make a fresh start who gets suckered into financing Prospector Pan Taggart's expedition into Injun Country to find the mother lode in Gold Creek.
- In The Outlaws IS Coming!, magazine editor Kenneth Cabot (Adam West) is a greenhorn who gets from Boston to the Wild West to investigate the vanishing buffalo herds. Despite not knowing one end of a gun from the other (his first on drawing the gun he bought for the journey is to peer down the barrel), he is Framed for Heroism by Annie Oakley and becomes Sheriff of Caspar.
- Winnetou: In one form or another, this is what Old Shatterhand repeatedly gets mistaken for as a plot point even long after he's become famous in the West under that name. Mostly because he actually does buy clean new clothes and the like every so often, uses his nom du guerre only when he means to impress (and his plain old German given name otherwise), isn't above sometimes coming up with a quick fib about his identity for various reasons, and of course for all the fame attached to his name most people still simply don't know what the actual man behind it actually looks like. And what he looks like is actually not very impressive - an unassuming, average-sized, friendly and polite young man, with hands that seem to be "as delicate as a woman's" does not exactly lead a seasoned westman to believe this is Old Shatterhand, who everybody imagines to be at least a 7-feet tall mass of muscles. (He also explicitly begins his future career in the West as a "greenhorn" — using that very word — in Winnetou I.)
- Randy Discher, in the episode of Monk where he quits the force to take over his uncle's farm.
- Amos Garrett in Deadwood is a perfect example of the first type. He is even literally referred to as "The Dude".
- Simon in Firefly. One of the things unfortunately cut short was his potential to develop from this trope into a conman able to use his familiarity with the Alliance, respectable appearance and intelligence to pull jobs the border-dwelling rest of the crew couldn't otherwise pull off (for example, the hospital job in Ariel).
- The cowboy song "Zebra Dun" is about someone mistaken for this. In it, a well-dressed fancy-talkin' man approaches a cowboy camp asking if he can borrow a horse. The cowboys give him the titular Zebra Dun as a prank, it being the worst bronco anyone's ever seen. The newcomer rides him like he was on a palfrey going to town, even letting go the reins to roll a cigarette while the horse bucks. The impressed foreman immediately offers him a job.
- Lots of them in Deadlands, of all types.
- In Red Dead Redemption, John comes across a writer from the East named Jimmy Saints, who's writing stories about the West. He's later encountered several times inexplicably captured by gangs of outlaws. Eventually he decides to just go back home and write about something else (presumably something that won't get him killed).