Definition - What does Manu mean?
Manu, according to Hindu mythology, is the name given to the progenitor of humanity. Manu is believed to be the first to appear during the beginning of each kalpa (or "aeon") and after the destruction of the universe. In the Bhagavad Gita, each kalpa is considered to be a period of 4,320 million human years.
Manu is also the author of Manusmriti, which means "Manu's laws/rules." Manusmriti is believed to be the word of Brahma, the Hindu creator of the universe. Hinduism holds Manusmriti in high esteem, classifying the work as the authoritative statement on the principles of dharma (the Sanskrit word for "duty" or "law").
Yogapedia explains Manu
It is believed that Manu gave life to all humans following his appearance in the world which was made possible by God. According to Hindu mythology, 14 Manus appear during a kalpa and the period of each Manu is referred to as manvantara.The world's current kalpa is the aeon of the white boar, or vaivasvata. It is the seventh kalpa this world has seen.
In Bhagavad Gita, Lord Vishnu says that he preached the knowledge of yoga to the sun god and he, in turn, preached it to Vaivasvat Manu, his son and the first of the human race.