megavoltage
/ˈmɛɡəvəʊltɪdʒ/ /ˈmɛɡəvɒltɪdʒ/Medicine
noun
Voltage exceeding one million volts, specifically as used in the generation of therapeutic radiation. Chiefly attributive Compare orthovoltage, supervoltage.
Origin
1950s; earliest use found in Nature: a weekly journal of science. From mega- + voltage, after megavolt.