From Longman Dictionary of Contemporary Englishmissivemis‧sive /ˈmɪsɪv/ noun [countable] literary TCMa letter – often used humorously An anonymous missive had been pushed under her door.
Examples from the Corpus
missive• His main activity is running to the mailbox to look for missives from his beloved.• Even now, her missive was not long and, as if to aid its content, was accompanied by a family photograph.• He recited the indignant missive about the kippers and toast.• Users can send as many love missives as they like, one at a time.• Equally intriguing are the missives from my brother, the newspaper cuttings that arrive every three weeks or so.• The missive points out that the Web is getting faster and easier to use, giving people more access to multimedia creativity.• Neil Kinnock has been sent three Tyler missives and responded, albeit in plain prose.• If your missive is addressed to your colleagues, then jargon may be acceptable shorthand.Origin missive (1500-1600) French lettre missive “letter intended to be sent” 