1. Pokémon. A system introduced in the 6th Generation of Pokémon RPG titles, Pokémon X & Y, that allows a player to connect to the Pokémon Global Link and trade away any Pokémon for a random Pokémon from a random player that also chose to participate in such a random trade.
EX. Wonder trading is probably one of my favorite new features of X & Y but, like any system that lacks any sort of moderation, the users abuse it.
Ideally, someone puts a Pokémon that is hard to find, evolves through trading, is version exclusive, has good EVs/IVs and/or abilities and/or moves, or is shiny/special in some such manner up for trade in hopes of receiving, at the very least, a Pokémon of foreign origin. Instead? Well, you trade a Fennekin you hatched on Wonder Trade and wind up with a Pidgey.
To be fair, I do accept one other type of Wonder Traded Pokémon-- if you give it a funny name and/or moveset, I would give the trade a pass. It's kind of fun to receive a clever little joke from someone, especially if it can level up faster.
As for myself, I've traded version exclusives, hard to get Pokémon, and about six Stunfisks named "Flat Stanley" after the children's book/activity character where children make a construction paper Flat Stanley, send him through the mail to some business or distant place, and get him back with photos of his "adventure". I dunno, I think it's funny. Shrug.
So far, in Wonder Trade, I've received some really cool foreign Pokémon including a German Tyrunt and a French Fennekin, so it's not all bad. It really makes me think a Wonderlocke challenge could be fun, but that's a discussion for another day.