IPA: /ɪnˈdiːsənt/
KK: /ɪnˈdisənt/
Not proper or acceptable according to social standards; often related to behavior or appearance that is considered offensive or inappropriate.
The movie was criticized for its indecent content that many found offensive.
Indecent is formed from "in-" (meaning not) and "decens" (from Latin, meaning proper or decent). The word describes something that is not proper or inappropriate.
Think of 'not' ('in-') being combined with 'proper' ('decens') to remember that 'indecent' means something that is not proper.