We were deeply frustrated that the meeting was canceled without explanation.

frustrated 是动词 frustrate 的过去分词形式，frustrate 的意思是"使沮丧、挫败"。这里用过去分词形式表示被动含义，指"感到沮丧的"。 frustrate 由拉丁词根 frustr-（徒劳的）和后缀 -ate（使...）组成，字面意思是"使徒劳无功"，引申为"使受挫、使沮丧"。