Definition - What does Muni mean?
Muni can be translated to mean "he who is silent." It is related to mauna, which means "sacred silence" or "meditation." The Sanskrit term may be used for a sage, or sadhu, who has made a vow of complete silence or who speaks only exceptionally. Their silence is part of their search for stillness of mind.
A muni may also refer to a hermit, or someone who is naturally attracted to a life of spiritual desire and has no longing for money, home, family or status. In the context of yoga, it has been used to refer to yogis.
Yogapedia explains Muni
A muni is someone who is constantly committed to exploring the mysteries of nature, or someone who is constantly engaged in examining the real nature of life and its related problems through tapas (austerity or purification of the self). Being a muni is a step between being an ordinary person and a rishi, which is a saint who has realized truths and gained eternal knowledge.
In ancient yogic literature, especially in the oldest "Rig Veda," the term, muni, was also used as an early reference to yogis. It is believed that the munis in ancient India practiced yoga, austerities and rites as well as glorified a life of renunciation, isolation, wandering and begging.