is a compound term of muga and mushin

Mushin

Mushin is a mental state into which very highly trained martial artists are said to enter during combat. They also practice this mental state during everyday activities. The term is shortened from mushin no shin , a Zen expression meaning the mind without mind and is also referred to as the...

. Muga literally means no-self (derived from the Sanskrit

Sanskrit

Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 anātman

Anatta

In Buddhism, anattā or anātman refers to the notion of "not-self." In the early texts, the Buddha commonly uses the word in the context of teaching that all things perceived by the senses are not really "I" or "mine," and for this reason one should not cling to them.In the same vein, the Pali...

) and Mushin no-mind (also from the Sanskrit

Sanskrit

Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 a-citta). What is negated is the empirical body-mind

Body-mind

Bodymind is a compound of body and mind, which, in the New Age disciplines of humanistic psychology and spirituality, researchers in the second half of the twentieth century had begun studying in order to move beyond the dualist conceptions of body and mind towards a unified and interrelated...

 as an ontological independent state of existence

Existence

In common usage, existence is the world we are aware of through our senses, and that persists independently without them. In academic philosophy the word has a more specialized meaning, being contrasted with essence, which specifies different forms of existence as well as different identity...

. Muga and mushin point to the same thing, the state of egolessness, but from different perspectives. Muga refers to the negation of the physical state, mushin to the mental state of empirical

Empirical

The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 existence.

To understand better mushin one needs to understand acitta, or simply its Sanskrit

Sanskrit

Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

-root citta

Citta

Citta was one of the chief lay disciples of the Buddha. He was a wealthy merchant from Savatthi. His life and character were so pure that near his death, had he wished to be a chakravartin, it would've been granted. However, he turned down this wish as it was temporal...

.