1) A random person selling tickets to an event (sporting games, concerts, etc.) on the side of the road. Usually this person is normal and just trying to sell an extra ticket.
2) Inversely, a scalper is also the term used for a person who is trying to buy a ticket from someone on the side of the road. This person just showed up at the event, hoping that someone would be selling an extra ticket.
*When scalping, price negotiation is acceptable.
**Be aware that if you obtain/sell a ticket, the person who sold/bought the ticket from you will most likely be sitting next to you at the event (if the ticket has an assigned seat) because people typically buy tickets with the seats together. This will only happen if the person you bought/sold the ticket too will also be in attendance at the actual event.
Bob: Nope, but I'm going to get there early and try to scalp a pair.
Joe: Good call. You'll probably get them for cheap.
Bob: I know, right?
Joe: Just be careful the scalper you buy them from is okay, because you're going to have to sit next to him the whole game.
Bob: Good call.
Sarah: I have an extra ticket for the concert tonight because Mary can't come.
Becca: You should definitely scalp the ticket to get some cash.
Sarah: Good call.
Becca: Be sure you sell it to someone decent because we're going to have to sit with her the entire show.
Sarah: Good call.
In my defintion, and in the defintion of anyone who has ever had their potential ticket taken by a scalper, or has been forced to buy from a scalper: The absolute scum of the earth, worse than neo-nazis, telemarketers, and rapists combined. They lack the decency, intelligence and integrity to make an honest living, so they prey upon and exploit other peoples' love of music, sport and general interests.
Make sure you get your tickets before these cocksuckers do, and no matter how much it pains you to miss an event, NEVER buy from them - it is the only way to get rid of them - event organisers try to place measures to get rid of them, but they do very little. If nobody buys from a scalper, they make huge losses buying expensive tickets nobody used, and will be discouraged from doing it again. If you buy from a scalper, you're only supporting them and making the problem worse. Better yet, if you see one at a game/show/etc, punch them, spit on them, assault them, but watch out, ticket scalping organisations employ massive 300lb sellers for a reason.
2. If nobody buys from scalpers, they will make huge losses, and be forced to go back to their original occupations as glory hole employees