If you say that something is a figment of someone's imagination, you mean that it does not really exist and that they are just imagining it.
例句
The attack wasn't just a figment of my imagination.襲擊可不是我憑空想象出來的。
英漢詞典釋義
n.
虛構的事物
a figment of the imagination虛構的事
臆造的事物；虛構的事
Doctor, are you suggesting the pain is a figment of my imagination?醫生，你是說這疼痛是我想像出來的嘍？The figure vanished as silently as if it had simply been a figment of her imagination.那個人影無聲無息地消失了，仿佛一切只是她的憑空想像。