There have been some observed studies and developed applications (apps), with a concentration on Mobile Assisted Language Learning (MALL), and no consideration of communicative needs of the learners; besides, these studies focused on either the theoretical aspects or the utilization of the available apps in the market (Burston & Athanasiou, 2020). Hence, Vocabulary Guru (VG), a custom-made mobile application, was developed based on a critical framework and an agile approach to fill out the gap. To tackle the issue, after carrying out a qualitative needs analysis via interviews, the first version of the app was developed and released to the target intermediate EFL university students. The next iterations were developed interactively and creatively, in congruence with the feedback received from the target learners. This cycle of incrementing and re-coding of the app continued until the attractor basins superseded. In the current paper, to shed light on how dynamically the interaction between learners and developers can yield in applications, which are more user-friendly and appropriate for a unique pedagogical setting, the life cycle of VG has been discussed. The agile app development processes of the current study may be useful for vocabulary specialists, teachers, educators, app developers, and pedagogical foundations involved in or considering the design and development of mobile apps by critically analyzing the unique needs of the target population in an interactive dynamic, agile life cycle. The developed app (i.e., VG) may also be utilized by EFL learners who would like to learn academic vocabulary in an educational context.