演讲者突然偏离主题，开始谈论他最近的旅行经历。

The speaker digressed from his main topic and started talking about his recent travels.

digressed 是动词 digress 的过去式。digress 由前缀 di-（表示"离开"）和词根 gress（来自拉丁语 gradus，表示"行走"）组成，字面意思是"走开、偏离"。digress 指在讲话或写作中"偏离主题"，即"跑题"的意思。