Synonyms: unpremeditated
Definition: not prepared or planned in advance
Usage: asked an unpremeditated question
Similar words: unplanned
Definition: without apparent forethought or prompting or planning
Usage: an unplanned economy; accepts an unplanned order; an unplanned pregnancy; unplanned remarks
Synonyms: unpremeditated
Definition: not premeditated
Similar words: impulsive
Definition: without forethought
Usage: letting him borrow her car was an impulsive act that she immediately regretted