standard molality, \(m^{\unicode{x29B5}}\), \(m^{\,\unicode{x26ac}}\)

https://doi.org/10.1351/goldbook.S05918
Chosen value of molality and usually equal to 1 mol kg-1.
Source:
Green Book, 2nd ed., p. 54 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)