défi = challenge you either take a challenge, that means you will try and do your best to achieve or reach your goal. Or you challenge someone to compete against you or to try and do something you think they can't do. The same in French: Je me suis lancer un defi: arreter de fumer avant un mois Je te défie de sauter en parachute. In a larger sense, it also means to provoke or go against some authorities: Le voleur s'est introduit dans les bureaux de police sans être vu pour défier la justice. Cet enfant rebelle défie l'autorité de ses parents, il n'en fait qu'à sa tête. In no case the word defi will mean to refuse to submit, but mostly to provoke someone or something in order to check someone's authority or ability to do something. For example, when you challenge the power in place, it does not mean you don't submit yourself to it, but mostly to make it react in a way that will either show that they can control you or that they can't keep the control.