This study explored the notion of flow, which refers to a person's sense of being completely absorbed in a task, as it applies to second language (L2) learning and use. Previously, flow has been mainly examined through researcher-generated descriptions to which learners reacted using Likert-type scales. In this study, we examined flow through the perspectives of the individuals experiencing it, by asking them to describe any insights relevant to their experience. During four weeks, five undergraduate students taking L2 French or Spanish coursework reported their flow states in weekly diary entries and interviews. Students described a total of 15 flow states, reporting them most frequently in interaction inside and outside coursework (e.g. speaking to a friend/stranger, in a paired task) but also while taking an exam, studying grammatical forms, listening to a lecture, reading, and practicing a speech. Qualitative coding revealed seven dimensions of flow, where five previously reported dimensions (attention, interest, enjoyment, sense of accomplishment, skill-challenge balance) were supported and clarified through our analyses while the remaining two (oblivion, stress) were identified for the first time. Flow appeared to be linked to proceduralisation of L2 skills, as the element of automaticity was prominent in most descriptions of flow.