Adjective before the name of an extensive quantity generally meaning division by amount of substance to make it intensive. Molar volume is volume divided by amount of substance. In a few special cases molar is used to denote division by amount concentration (e.g. molar absorption coefficient).
Green Book, 2nd ed., p. 7 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 982 (https://doi.org/10.1351/pac199668040957)