Buang is a Cebuano word for crazy. Cebuano is a local dialect in the Philippines. Buang is typically a harsher word than crazy. This can be used as a curse when you are angry and can be used in tandem with other known Cebuano cuss words such as the likes of Yawa, Pisti and Atay.
Buang ka = You are crazy.
Yawa man diay ka, buanga ka. = Roughly translates to: You fucking evil, crazy asshole.