Medical professionalism is a core component of medical education, yet it remains conceptually ambiguous and inconsistently articulated across institutions, cultures and training contexts. Although students are expected to demonstrate professionalism as part of professional identity formation, the meanings and expectations associated with professionalism are often implicit, variable and shaped by both formal curricula and the hidden curriculum. This qualitative study examined how medical students articulate and make sense of professionalism during undergraduate medical training using a discourse-informed analytical approach. All students (M1–M4) at a single US medical school were invited to participate, and recruitment concluded after 44 students volunteered. Data were collected through 20 individual semistructured interviews and four focus groups, and transcripts were analysed inductively to identify recurring ways professionalism was articulated in students’ accounts. Analysis revealed three recurring ways professionalism circulated in student discourse: (1) definable and actionable, in which professionalism was described through observable behaviours such as punctuality, dress and communication; (2) inherently subjective, where professionalism was framed as situational, relational and shaped by cultural or interpersonal expectations; and (3) uncertain and confusing, characterised by difficulty articulating a coherent understanding and by the expansion of professionalism into broader expectations of self-presentation and image management. Across these accounts, students most often articulated professionalism in physician-centred terms, emphasising self-regulation, appearance, composure and evaluability, reflecting the institutional and assessment contexts of early medical training. This study demonstrates that medical students encounter professionalism through multiple coexisting ways of understanding that circulate within medical education and are variably taken up as students navigate professional expectations. By shifting analytical attention away from defining what professionalism should be and toward examining how professionalism is articulated and taken up in practice, a discourse-informed approach offers a productive framework for understanding professional identity formation in contemporary medical education.