at liberty   (TTS發音)

1. at leisure；unoccupied 閒著；無事

    I'll be at liberty after midday. 我午後有空。

2. free； unconfined不受約束；有行動或處理某事的自由

    You are at liberty to use the laboratory. 你可以自由地使用這個實驗室。

    The prisoners were set at liberty. 犯人被釋放了。