Emily Dickinson Lexicon

A'GI-O, n. [Ital. aggio, surplus, difference.]

1. In commerce, the difference between bank notes and current coin. In Holland, the agio is three or four per cent; in Rome, from fifteen to twenty five per cent; in Venice, twenty per cent, but the agio is subject to variation. – Encyc.
2. Premium; sum given above the nominal value. – Lunier.