"Civilian casualties" refers to the innocent people who are harmed or killed during a conflict or war. They are non-combatants, such as men, women, and children who are not involved in fighting or military activities. Full definition
For certain critics, even one civilian casualty incurred in a campaign designed to save lives will be viewed as too many. (blog.politics.ox.ac.uk)
The resignation of the Foreign Office minister will be a huge embarrassment for Cameron, who was warned recently that centrist Tories were uncomfortable with his unwavering support for Israel despite the extent of civilian casualties in Gaza. (politics.co.uk)
UNHCR reported in 2015 there estimates of civilian casualties in the Syrian conflict but didn't specify who killed them (politics.stackexchange.com)