To use Blastard means to insult someone beyond comprehension. To put it in simple terms, it insults how you were born, your parents, your life, your friends, your life choices, and just you as a person in general.
Boy 1: Lol you have no friendsloser Boy 2: You better watch it before you get blastard'
(Audience): OH SHIT HE BOUT TO BLASTARD THAT FOOL
Boy 1: Yo I'm sorry dude I didn't mean it
Boy 2: Its too late
(Audience): RIP my nigga
One who blares rap music at full volume with all windows open in his car, much to the annoyance of anyone else in a 30-foot radius.
Often two blastards will get into a volume war with their music, leading to a horrid-sounding mishmash of rap beats and cuss words that you can't keep from assaulting your ears even if you close your windows.
My drive from Atlanta to Orlando was plagued by the presence of a blastard that stuck by me on the highway the whole time. Now there's 8 hours I can't get the fuck back.