A day where you just want to break something, preferably something that will scream and/or bleed as you do it. You may or may not know of any direct causes, but most often, something bad happened early in the day which started you off in a generally bad distemperment that only got worse as multiple unfortunate events compounded to effectively gang-rape and murder your overall disposition.
Your bet bet is to stay away motherfucker, it's just one of those days.
Ulzzang true definition is "best & "face" = best face in korean. They are basically people with above average looks, sometimes with the use of photoshop and haduri who post their pics online, some becoming internet celebrities.
"Hey, see that chick over there? She's pretty enough to be an ulzzang. :D"