उपपौर्णमासिupapaurṇamāsiमासम् [māsam], मासम् ind. just preceding or at the time of the full-moon day.
मासम् māsam, मासम् Indeclinable just preceding or at the time of the full-moon day.
कोशःDictionaries
V. S. Apte, The Practical Sanskrit–English Dictionary. Look up any word of the Gita in Devanagari, IAST or Harvard-Kyoto, or browse the headwords letter by letter.