(n.) An unexpected and untoward accident; something inopportune or embarrassing; a hitch.

accessary accessory accidental addendum addition adjunct adventure appendage appurtenance auxiliary blow blunder calamity casualty cataclysm catastrophe chance chance hit collateral collision coming to be contingency contingent contretemps crack-up crash destiny disaster event eventuality eventuation extra fate fluke fortuity fortune freak accident grief hap happening happenstance hazard ill hap incidence incidental inessential kismet long odds long shot luck lucky shot materialization mere chance misadventure mischance misfortune mishap mistake nasty blow nonessential not-self other pileup realization secondary serendipity shipwreck shock smash smashup staggering blow subsidiary superaddition supplement tragedy unessential wreck