The term given to one who thinks they are the expert in everything beer related. Much like a wine connoisseur, though this arsehole individual differs in the way that they won't actually suggest a tastier beverage, just tell you that the one that you're drinking is shit.
BW: Hey dude, is that a Budweiser you've got there?
You: Sure is man, why do you ask?
BW: Budweiser is shit, all lagers are shit, ale is shit and so is stout.