SO just what does this adjective "Kafkaesque" mean? And why does Frederick R. Karl, author of an exhaustive critical biography of Franz Kafka, believe that the word is as misused as it is used? Kafka is the only 20th-century literary figure whose name "has entered the language in a way no other writer's has," Mr. Karl says. But "what I'm against is someone going to catch a bus and finding that all the buses have stopped running and saying that's Kafkaesque. That's not."