yoyo /jəʊ $ joʊ/ interjection especially American English informal 
used to greet someone, to get their attention, or as a reply when someone says your name: 
Yo, dude! How’s it going? ‘Darren?’ ‘Yo!’
used to greet someone, to get their attention, or as a reply when someone says your name: Yo, dude! How’s it going? ‘Darren?’ ‘Yo!’