1. [adj]  not intentional; "an unintended slight"; "an unintentional pun"; "the offense was unintentional"; "an unwitting mistake may be overlooked"
2. [adj]  without apparent forethought or prompting or planning; "an unplanned economy"; "accepts an unplanned order"; "an unplanned pregnancy"; "unplanned remarks"

UNPLANNED is a 9 letter word that starts with U.