Power Failure

I find it unbelievable, Perhaps a little mystical That Oxford and Webster are perplexed. Their lack of info leaves me vexed. Their reservoir of words is vast. They've never failed me in the past. Ligure simply is not in there. Nor does quadrivial appear. I know it's multiplied by four, But neither tells me any more. If f I had taken chemistry, All of these might be clear to me. I thought an instrument at sea, A pericope would prove to be. It's defined as short words of verse. I've written them, some bad, some worse. Written 7/17/18