When I first saw a fashion show at age 10, I was in a dream the entire time.

was 是 be 动词的过去式，表示"处于某种状态"。 in 是介词，表示"在...状态中"。 a 是不定冠词，表示"一个"。 dream 是名词，意思是"梦、幻想"。 was in a dream 这个短语字面意思是"处于梦境中"，引申为"心不在焉、恍恍惚惚"的状态。