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 वेपनम्
वेपनम्vepanamTremor, trembling.
[वेप्-ल्युट्]
Tremor, trembling.
Shaking, brandishing (the cord of a bow); Rām.1.67.1.