To willfully act in a reckless, foolish, and/or dangerous manner. Alludes to the literal act of running with a pair of scissors in one's hand, which can cause severe injury. I went through a really rebellious phase in high school and made a point of constantly running with scissors, so to speak, as a way of acting out. Jane's daughter has run with scissors so frequently by now that the family doesn't try to keep her under control anymore.