An ally is an individual who actively and continuously strives towards promoting justice and ending marginalization.
According to the Guide to Allyship, to be an ally is to:
The Anti-Oppression Network defines allyship by what it is not:
"allyship is not an identity—it is a lifelong process of building relationships based on trust, consistency, and accountability with marginalized individuals and/or groups of people; allyship is not self-defined—our work and our efforts must be recognized by the people we seek to ally ourselves with." From the College of DuPage LibGuide, What Is Allyship
Further Reading:
Patel, Viraj S. "Moving Toward an Inclusive Model of Allyship for Racial Justice." The Vermont Connection 32, no. 1 (2011): 9. https://scholarworks.uvm.edu/tvc/vol32/iss1/9/
Sue, Derald Wing, Sarah Alsaidi, Michael N. Awad, Elizabeth Glaeser, Cassandra Z. Calle, and Narolyn Mendez. "Disarming Racial Microaggressions: Microintervention Strategies for Targets, White Allies, and Bystanders." American Psychologist 74, no. 1 (2019): 128. https://doi.org/10.1037/amp0000296