What is "shambuka"

Shambuk ( Sanskrit śambūka) is, in Hindu mythology, a character in some versions of the Ramayana. According to that version, Shambuk, a shudra ascetic, was slain by Rama for attempting to perform penance in violation of dharma, the bad karma resulting from which caused the death of a Brahmin's son. It is believed that Shambuk was beheaded in a hill at Ramtek, near Nagpur in Maharashtra.