IPA: /ˌɪn.kəˈmjuː.nɪ.kə.tɪv/
KK: /ˌɪnˌkəmjunɪˈkeɪtɪv/
Not willing to talk or share information; quiet and reserved.
The incommunicative student rarely participated in class discussions.
Incommunicative → It is formed from "in-" (meaning not) and "communicative" (from Latin "communicativus", meaning sharing or imparting). The word describes someone who is not inclined to share or communicate information.
Think of someone who is 'not' ('in-') 'sharing' ('communicative') — that's why incommunicative means not willing to communicate.