This study developed a conceptual model of hierarchical microaggression phenomena in colleges and universities in the United States. Young, Anderson, and Steward coined the term "hierarchical microaggression" in 2015, which refers to microaggression towards defenceless and less powerful stakeholders. Because the hierarchical microaggression concept shares similarities with various forms of microaggression and bullying in hierarchical structures' power dynamics, this study reviewed literature pertaining to microaggression and bullying incidents in higher education settings. Among 187 articles located, approximately 61% (115 articles) demonstrated these phenomena. Through the lens of Bolman and Deal's four organizational frames -- structural, human resource, political, and symbolic -- a synthesis of the literature identified factors that shape the phenomena's conceptual model. The model showed that individuals who hold inferior or lower-ranked positions in colleges or universities often are victims of hierarchical microaggression; further, regardless of demographic characteristics, anyone can be either a victim or a perpetrator, while stakeholders from socially marginalised backgrounds tend to be victimised, regardless of their position. Hierarchical microaggression incidents tend to be justified in the name of supervising or mentoring (human resource frame), institutional policies (structural frame), and an institution's tradition or culture (symbolic frame) as a result of limited resources or perpetrators' positional power (political frame). This study articulates the unspoken realities behind such incidents, and suggests best practices and future research to prevent such incivility and cultivate diversity, equity, and inclusion on college campuses.