unplanned without apparent forethought or prompting or planning; "an unplanned economy"; "accepts an unplanned order"; "an unplanned pregnancy"; "unplanned remarks"
accidental,
inadvertent happening by chance or unexpectedly or unintentionally ; "with an inadvertent gesture she swept the vase off the table"; "accidental poisoning"; "an accidental shooting"
uncaused,
causeless,
fortuitous having no cause or apparent cause; "a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as...uncaused and unrelated to the times"
