(definitions from Dictionary.com)
21. to speak or behave with sudden anger, outrage, or the like
(often fol. by out): to flash out at a stupid remark.
That sudden angry punch or plate thrown against a wall often feels
out-of-place within the confines of flash. Of course, anyone can make anything
work in a flash fiction piece. But flash sometimes works best to capture the
unrealized sudden outburst, focusing instead on something more subtle.