"Turned the key" can be synonymous with starting, igniting, activating, or unlocking something. However, if we are looking for antonyms for this phrase, we can consider terms like "disengaged," "halted," or "disabled." These antonyms indicate the interruption or cessation of a process or action that was initiated by turning the key. Other antonyms for "turned the key" could include "closed," "sealed," or "locked," which refer to actions that prevent access or movement rather than initiating it. Ultimately, the choice of antonym will depend on the specific context and intended meaning of "turned the key.