Yet Another Funny Message. Also heard as YAFMC ("...Message Combination"). This is used in rec.games.roguelike.nethack to describe really interesting messages that were seen when playing Nethack.

Example of YAFM (more like "yet another morbid message", though): "Time stands still as you and Barney the Dinosaur lie in each other's arms..."

Some more:

"Core dumped."

(This message is displayed if you eat an apple or pear in UNIX version...)

"You see here an ape corpse. It bites your foot!"

(Nethack just says "it" if the monster is invisible. In this case, some invisible bugs are trying to eat your legs...)

"You decide not to force the issue."

(Illogical use of #force command.)