The full title, seen mostly on printed Bibles; in speech it is 旧约. With the 新约全书 (New Testament) it makes up the 圣经. 约 here means 'covenant'.
culture
Protestant and Catholic Bibles in Chinese name many people and books differently: Moses is 摩西 in the Protestant 和合本 but 梅瑟 in Catholic editions, and Genesis is 创世记 in one and 创世纪 in the other.