Implementation of Professional Learning Communities (PLCs) has become common place in schools across the globe. Perhaps, the prevailing definitions and operationalization of PLCs could explain the disparities in how they are executed in various contexts. By investigating a selection of recent studies, this review of literature aims to analyse how PLCs have been defined and operationalized in contemporary research. A total of 70 quantitative and mixed-methods research studies that were conducted between 2013 and 2018 were chosen to be inspected in this review to identify the definitions and tools employed in those studies. The definitions and tools were identified and analysed qualitatively to examine the underlying concepts. Findings of the investigation revealed that the definitions of PLCs were composed of three major components; "process, outcome" and "critical conditions." Moreover, it has also been found that Professional Learning Community Assessment (PLCA) and its revised version PLCA-R were the predominant operationalization of PLCs in the recent years. The findings advocate the need for ensuring critical conditions for sustained implementation of PLCs. It is also claimed that inclusion of "result orientation" as a new dimension might demonstrate a better operationalization of PLCs.