noun · a derogatory term used to refer to foreign invaders

在那段动荡的历史中，老百姓常把入侵者称为鬼子。

noun · a derogatory term specifically for Japanese soldiers or people, particularly during the War of Resistance against Japanese Aggression (1931–1945)

爷爷经常给我们讲他当年在游击队打鬼子的故事。