"I guess that makes sense," Crowley mutters. If he thought to tell Susan, she would most likely be fascinated that Noo-boh has become a multi-dimensional being, having gone off with an alternate universe version of Lan Wangji and somehow at the same time, stayed with SecUnit. It makes perfect sense to him, so he doesn't. "Well, ineffability means it can't be described by the human language. So an ineffable marriage is one that's sort of... er, written into the code. Incomprehensible for a thousand years until two idiots suddenly wise up. You know?¹"

¹She does not, that wasn't the best definition.