What is "raghu"

Raghu was a ruler of the mythological Ikshvaku dynasty. According to the Raghuvamsha, he was born to king Dilīpa and his queen Sudakshina. His name in Sanskrit means the fast one, deriving from Raghu's chariot-driving abilities. So celebrated were the exploits of Raghu, that his dynasty itself came to be known as the Raghuvamsha or the Raghukula after him. The history of his dynasty is elaborated upon by Kalidasa in his Raghuvamsha.