Muzungu is a word from the languages of Kinyarwanda and Kirundi meaning "white person" (pl. 'bazungu'). It is closely related to the Kiswahili word 'mzungu', with which it is often confused by Westerners. A derivative is the derogatory 'kazungu' meaning 'little white person'.
hey you mzungu - hey you white man