1. A plot or compact made by persons who swear to each other to do something that will result in public harm.
2. The offense of attempting a conference with evil spirits to discover some secret or effect some purpose; witchcraft; sorcery.
“Coniuration (coniuratio) is the very French word drawne from the latine, which as it is compounded of (con & iuro) so it signifieth a compact or plot, made by men combining themselves together by oath or promise, to do some publique harme. But in our common lawe, it is especially used for such as have personall conference with the devill or evill spirit, to know any secret, or to effect any purpose. And the difference that I have observed (how truly let those judge that be beter skilled in these maters) betweene coniuration and witchcraft, is because the one seemeth, by prayers and invocation of Gods powerfull names, to compell the devill, to say or doe what he com-mandeth him: the other dealeth rather by a friendly and voluntarie conference or agreement betweene him or her and the devill or familiar, to have her or his desires and turnes served in lieu of blood, or other gift offered unto him, especially of his or her soule.” John Cowell, The Interpreter (1607).