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.
Entry दिवम्
दिवम्divamHeaven.
[दीव्यत्यत्र घञर्थे आधारे क]
Heaven.
The sky; see दिव्; दिवं ते शिरसा व्याप्तम् Mb.12.47.88.