Although other answers are acceptable, the general term applied to “脱調” is “pull out”.　“脱調” is also known as “同期外れ”, which is termed “pull out” or “step(-)out” in English. It generally means that two or more synchronous machines or systems can no longer be rendered operative because of gradual increase or sudden change in their load. In the synchronized state, however, these machines or systems should be in operation in the same cycle or at the same speed.
One of examples:
Although the dc-excited motor has a squirrel cage for starting, the inherent low starting torque and the need for a dc power source requires a starting system that provides full motor protection while starting, applies dc field excitation at the proper time, removes field excitation at rotor pull-out, and protects the squirrel-cage winding against thermal damage under out-of-step conditions. (Source:　MACHINE DESIGN Magazine [USA])