The ability to withstand the test of time, even to the point of coming back from apparent extinction.
Some words refuse to be relegated to linguistic history books -- like the Ivory Billed Woodpecker, they seem to ressurect after years of disuse, showing remarkable sticktoitiveness.
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"