The belief that life is inherently negative, and therefore should be voluntarily ended. Efilists do believe in people's rights to choose for themselves however, and would not support a genocide of all life. In an efilist's ideal world, every human on earth would commit suicide, ridding the world of what they see as the plague of human life.
"Did you hear Johnny killed himself?"
"Oh my god! Why?"
"He said in his note that it was something to do with this philosophy of his called efilism. He urges us to kill ourselves as well."
"Wow, that's dark."