Yamāntaka is a Sanskrit name that can be broken down into two primary elements: Yama, the name of the god of death; and antaka, or "terminator". Thus, Yamāntaka's name literally means "the terminator of death".
Within Buddhism, "terminating death" is actually a quality of all buddhas as they have stopped the cycle of rebirth samsara. In this context, Yamantaka represents the goal of the Mahayana practitioner's journey to enlightenment, or the journey itself: in awakening, one adopts the practice of Yamāntaka – the practice of terminating death.
"Yamantaka" or "Shri Bhagavan Yamantaka" (Glorious Lord Making an End of Yama*) is another name for [Shri] Vajra[maha]bhairava, who is the highest emanation of Bodhisattva Manjushri. Bodhisattva Manjushri, Shri Vajrabhairava and Shri Bhagavan Yamantaka together represent the [Buddha]dharmakaya (Body of [Enlightened] Doctrine) which is also called Vajradhara (Holder of the Thunderbolt) because it holds to the pledge of the thunderbolt (vajrasamaya) which is the pledge to carry out the action of the Buddha.
There are three types of death spoken of in the Yamāntaka Tantra : Outer death is the regular end of life, which is embodied by Yama, Lord of Death, who resides in the south, seven stories under the earth. The inner death is misknowledge of reality, which is instinctive clinging to objectively real objects and subjects. The secret death is dualistic appearance on the subtelest level of clear light mind and illusory body. With the practice of Yamāntaka one overcomes those types of death and gains immortality as a buddha.