RPG.net lexicon defines it as:

Illegitimate enjoyment. Saying that a game is "bad wrong fun" indicates that the game is somehow broken, unplayable, poor quality or weak - in ignorance of the fact that many groups are playing and enjoying it regularly. As such, this is not normally something that a person will say themselves, but something they will accuse other people of having said. For example, "John said that d20 is bad wrong fun" indicates that the speaker believes John's criticism of d20 to be foolish given the large number of groups playing and enjoying it. Rifts is often cited as a "bad wrong fun" game. Often written as a single word, badwrongfun.

 

"Bad wrong fun" is also often used in a more light-hearted sense to indicate the gamer equivalent of a guilty pleasure. "I know it's bad wrong fun, but I loved every minute of it!"

The earliest reference I can find to its usage is from RPG.net in 2004.

The question interests me as it is clearly a concept that is not peculiar to role playing games. For example, football matches could be badwrongfun for people who prefer opera. As such I have posted this question on our sister site English Language & Usage to find out what other terms exist for the phenomenon.

RPG.net lexicon defines it as:

Illegitimate enjoyment. Saying that a game is "bad wrong fun" indicates that the game is somehow broken, unplayable, poor quality or weak - in ignorance of the fact that many groups are playing and enjoying it regularly. As such, this is not normally something that a person will say themselves, but something they will accuse other people of having said. For example, "John said that d20 is bad wrong fun" indicates that the speaker believes John's criticism of d20 to be foolish given the large number of groups playing and enjoying it. Rifts is often cited as a "bad wrong fun" game. Often written as a single word, badwrongfun.

"Bad wrong fun" is also often used in a more light-hearted sense to indicate the gamer equivalent of a guilty pleasure. "I know it's bad wrong fun, but I loved every minute of it!"

The earliest reference I can find to its usage is from RPG.net in 2004.

The question interests me as it is clearly a concept that is not peculiar to role playing games. For example, football matches could be badwrongfun for people who prefer opera. As such I have posted this question on our sister site English Language & Usage to find out what other terms exist for the phenomenon.