atrocity
Concise Oxford English Dictionary © 2008 Oxford University Press:
atrocity/əˈtrɒsəti/
▶noun (pl. atrocities) an extremely wicked or cruel act.
– origin C16: from Fr. atrocité or L. atrocitas, from atrox, atroc- ‘cruel’.
'atrocity' also found in these Oxford entries:

