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.
tadā gantāsi nirvedaṁ śrotavyasya śrutasya ca. — When thy intelligence shall cross beyond the whirl of delusion, then shalt thou become indifferent to Scripture heard or that which thou hast yet to… 2·52
गन्तासिgantāsinominative singular of the verbal noun gantṛ (one who goes) with the Present 2nd Person Singular of the Verbal root as (to be) joined to it in order to give it the sense of the future tense (thou shalt attain).