In North Korea, ㅉ is called 된지읒 (doenjieut), "strong ㅈ (jieut)". In South Korea, it is called 쌍지읒 (ssangjieut), "doubled ㅈ (jieut)".
ㅉ is pronounced as an alveolo-palatalaffricate with tensephonation (IPA: [t͈ɕ] or [d̬ʑ]), i.e. similar to the English ch, but with a stiff tongue and glottal opening.
In Dongguk Jeong'un (東國正韻), this letter was used to transcribe voiced alveolar sibilant affricate ([d͡z]) of Middle Chinese.