Slang, explained by the people who actually use it.

It is an abbreviation of "suddenly pops out."

Short for "knife-sharp clock-out" — leaving work exactly on time, the minute your hours end.

"Mom's friend's son" — used for someone impossibly accomplished compared to you. The female form is "eomchindal" (mom's friend's daughter); there's also "bu-chinnam" (wife's friend's husband).

A cute word for a dog — 멍멍이 ("woof-woof") rewritten as look-alike letters 댕댕이.

From the CORTIS song "Young Creator Crew" — someone (of any age) with fresh, trend-savvy taste. The opposite is 늙크크.

Short for "good feeling" — something has a nice vibe.

"Are you a T?" — teasing someone for answering with cold logic instead of empathy, after the Thinking (T) type in MBTI.

Short for "default camera, no editing" — used to stress that a photo was taken with the phone's stock camera and not retouched.