Definition from Wiktionary, the free dictionary
yobo (plural yobos)
- (slang, Australia) Someone, usually a male, who is uncouth, badly behaved and obnoxious. Loud and drunk are also characteristics, but not always present.
- (slang, UK) A cruel and brutal fellow.
Usage notes 
- Yobo, 20th Century Words, by 艾托, John Ayto, Oxford University Press, 2002, Page 224.
- Yobo, http://www.thefreedictionary.com/yobo
Hawaiian Pidgin 
- A Korean person