Numerous real-world studies have shown that the monitoring of feeding intolerance (FI) is necessary to ensure that enteral nutrition (EN) is successful, and is recommended by the main international nutrition guidelines and expert consensus as a core item to evaluate EN implementation. However, there is still no unified clinical definition or criteria about FI at present, which leads to difficulties in results interpretation of relevant research, hindering effective evaluation of approaches for FI preventing or treatment as well as impeding further study in more depth. We review literatures on how to define FI and put forward outcome-centered concept of FI symptom group, to provide a novel idea for understanding and defining clinical FI.