To agree, by oath, covenant or otherwise, to commit a crime; to plot; to hatch treason. The servants of Ammon conspired against him, and slew the king in his own house. 2 Kings 21:23. They conspired against Joseph to slay him. Genesis 37:18.

In law, to agree falsely and maliciously to indict an innocent person of felony.

To agree; to concur to one end. The press, the pulpit, and the stage, conspire to censure and expose our age. All things conspire to make us prosperous.