During his important presentation, he suddenly lost his voice.

lost 是动词 lose 的过去式，lose 的意思是"失去、丧失"。 his 是代词 he 的所有格形式，意思是"他的"。 voice 的意思是"声音"，指人说话或唱歌时发出的声音。 lost his voice 是一个固定搭配，字面意思是"失去了他的声音"，实际指"突然说不出话"或"失声"的情况。