Over the past few decades, moral distress has been examined in the nursing literature. It is thought to occur when an individual has made a moral decision but is unable to act on it, often attributable to constraints, internal or external. Varying definitions can be found throughout the healthcare literature. This lack of cohesion has led to complications for study of the phenomenon, along with its effects to nursing practice, education and targeted policy development.The aim of this analysis was to uncover unique definitions of moral distress as found in the nursing literature and to examine the relationship between these definitions.Morse's method of concept clarification was applied given the large body of literature which includes definitions, descriptions and measurements of the concept in research. The steps include (a) conducting a literature review; (b) analysing the literature; and (c) identifying, describing, comparing, and contrasting attributes, antecedents and consequences of each category.Each of the 18 included studies described constraints in their definition of moral distress, whether implied or explicitly stated. External constraints are widely described as obstacles outside of the individual, whether institutional, systemic or situational, while internal constraints are located within the individuals themselves and are described as personal limitations, failings or weakness of will.Upon reviewing these definitions, we determined that the term 'internal constraints' is problematic due to the emphasis of responsibility on the individual experiencing moral distress. We propose an alteration to 'internal characteristics' that will assume less responsibility of change from the individual to place a heavier onus on systemic and institutional constraints.