1.NounAn extremely cruel act; a horrid act of injustice.
"to carry out / commit / perpetrate an atrocity; The regime is guilty of mass atrocities including forced displacement and the use of chemical weapons."
2.NounThe quality or state of being atrocious; enormous wickedness; extreme criminality or cruelty.
3.NounAn object considered to be extremely unattractive or undesirable.