Circuit return - Common connection, specific potential difference.
All like-designated points are connected.
The asterisk is not part of the symbol. Identifying values, letters, numbers, or marks shall replace the asterisk.
(in English) (1993)  315-1975 - IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters), IEEE, p. 51  DOI:  10.1109/IEEESTD.1993.93397. ISBN:  0738109479.
Michel Bakni