What this means: ㅇㅊ ?
Of the short form of Hangul I know these:
ㅇㅇ [응] – Yes.
ㅉㅉ – tsk tsk (that clicking sound you do with your tongue when you are displeased with someone).
ㅇㅋ [오키] – Okay.
ㄱㅅ [감사] – Thank you.
ㅊㅋ [축하] – Congratulations.
ㄴㄴ [노노] – No.
ㅈㅅ [죄송] – Sorry.
ㄱㄷ [기다려] – Wait.
ㄱㄱ [고고] – Gogo.
ㅂㅂ [바이 바이] – Bye Bye.
ㄷㄷ [덜덜] – Trembling
ㅅㄱ [수고] – Well done / Good job.
ㅊㅊ = Congrats
ㅗㅗ = F*ck you
ㅡㅡ - WTF
ㅁㅊ - Crazy
ㅎㄹ - Daebak
짱 - Best, Top of top or Super
etc...