He always acts like he's being martyred just for working overtime occasionally.

martyred 是动词 martyr 的过去分词形式。martyr 原指"殉道者、烈士"，这里用作动词表示"表现得像殉道者一样"，带有夸张和戏剧化的意味，暗示某人故意表现出过度受苦或牺牲的样子。