Subtitles are a printed translation of the words of a foreign film that are shown at the bottom of the picture.
(电影的) 字幕
If you say how a book or play is subtitled, you say what its subtitle is.
给…加副标题 • "Lorna Doone" is subtitled "a Romance of Exmoor." 《洛娜·杜恩》的副标题是《埃克斯穆尔的一个浪漫故事》。