a·tro·cious [? tr?sh?ss] adjective 1. very bad: appallingly bad atrocious manners 2. very cruel: extremely evil or cruel atrocious crimes 3. ugly to look at: ugly in taste or appearance an atrocious hat [Mid-17th century. < Latin atroc- "fierce, cruel" < ater "dark"] -a·tro·cious·ly, adverb -a·tro·cious·ness, noun