The authors, healthcare professionals and bioethicists who collaborate on health system research, felt there was an undefined phenomenon occurring in practice. McAuley called it 'The Nike Clause' that is when faced in practice with a barrier that caused a moral dilemma, some health professionals’ solution was to 'just do it', take the action thought to be the 'right' thing to do despite the barrier. We philosophized whether this had a positive relationship to moral distress and how prevalent it might be across different clinical settings given their varying constraints on professional autonomy and differing barriers to care. We felt that to explore this further a conceptual definition of what we now term 'conscientious defiance' was necessary. To that end, in this work, we outline the concept of conscientious objection and its key elements. Using these key elements, we then set out to define conscientious defiance, describing similarities and key distinctions. We discriminate our concept from previously defined terms such as “workaround” (Berlinger, 2016) and “civil disobedience” (as it relates to health) (Childress, 1985) and suggest that conscientious defiance is novel and important. We then discuss whether a health professional has a right to conscientious defiance under conscience protections, exploring the arguments for and against. Lastly, we suggest that empirical work is needed to further understand conscientious defiance in practice and its relationships to moral distress and moral courage. There will be important ethical considerations in investigating a phenomenon that may be considered unprofessional and we raise some of these.