/məˈnɒθəˌlɪtɪzəm/
From Greek monos ("single") and thelēma ("will"). The term was coined for the 7th-century Christological heresy asserting that Jesus Christ had only one will, the divine will, rather than two distinct wills (one divine, one human).
Monothelitism is a heresy which posits that though Christ has two natures (divine and human), He has only a single will (the divine will). The orthodox doctrine, affirmed at the Third Council of Constantinople (681 AD), is Dyothelitism: that Christ possesses two distinct wills, a divine will and a human will, which always act in perfect harmony, with the human will submitting to the divine. This is crucial because for Christ to be a true and sufficient substitute for humanity, He must have a genuine human will capable of obedience, as demonstrated in His prayer in Gethsemane: "not as I will, but as you will" (Matthew 26:39).
MONOTHELITE, n. One who holds that Christ had but one will.
A modern, functional monothelitism appears in teachings that diminish the genuine humanity of Christ. This can manifest as a form of "superhero Jesus" theology that effectively denies His human struggles, temptations, and the real exercise of His human will in obedience to the Father. When we fail to appreciate that Christ had a human will that He willingly and perfectly submitted to the divine will, we rob His obedience of its power, undermine His example for us, and diminish His role as the sympathetic High Priest who was "in all points tempted as we are, yet without sin" (Hebrews 4:15).