Someone who likes to spend so long having sex that parts start chaffing and turning red. Named after a famous Baseball team who took so damn long to win people had DIED waiting for them.
Red Sox fans are people who believe that their inability to climax makes them great lovers as opposed to tedious ones.
"Oh my God, he kept going on and on, a total Red Sox fan!"
"Way! And you know what? Afterwards he was convinced I had just witnessed the best sex on Earth!"
"What a loser!"