Their attempts to keep the secret were ultimately defeated by a curious journalist.

defeated 是动词 defeat 的过去分词形式。defeat 由前缀 de-（表示"去除、破坏"）和词根 feat（来自拉丁语 factum，意为"完成的事"）组成，字面意思是"使已完成的事失效"，引申为"击败、挫败"。 在句中作为过去分词表示被动，defeated 指"被击败/被挫败"。