IPA: /ˌkɒn.tjuˈmeɪ.ʃəs/
KK: /kɒnˈtjuːmeɪʃəs/
Stubbornly refusing to obey rules or authority.
The contumacious student repeatedly ignored the teacher's instructions.
Contumacious → It is formed from "contumacia" (meaning stubbornness or disobedience) and the suffix "-ous" (meaning full of). The word describes someone who is full of stubbornness or rebelliousness, particularly in defiance of authority.
Think of someone who is 'full of' ('-ous') 'stubbornness' ('contumacia') — that's why contumacious means being rebellious or disobedient.
No commonly confused words.