IPA: /ɪnˈdɪsɪplɪn/
KK: /ɪnˈdɪsəplɪn/
A failure to follow rules or control one's behavior, often leading to disorder or chaos.
The teacher was concerned about the indiscipline in the classroom.
Indiscipline is formed from "in-" (meaning not) and "disciplina" (from Latin, meaning instruction or training). The word refers to a lack of discipline or failure to follow rules or training.
Think of 'not' ('in-') following 'instruction' ('disciplina') — that's why indiscipline means a lack of following rules or training.