ultimo

adverb

1. in or of the month preceding the current one: on the 12th ultimo. Abbreviation: ult., ulto.Compare instant(def 11), proximo.

adverb

1. (esp abbreviated in formal correspondence) in or during the previous montha letter of the 7th ultimo Abbreviation: ult. Compare instant (def. 7), proximo

“in the month preceding the present,” 1610s, common in abbreviated form ult. in 18c.-19c. correspondence and newspapers, from Latin ultimo (mense) “of last (month),” ablative singular masc. of ultimus “last” (see ultimate). Earlier it was used in the sense of “on the last day of the month specified” (1580s). Contrasted with proximo “in the next (month),” from Latin proximo (mense).